List of Publications by Dr. Alexey V. Fedorchenko, PhD

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Total published papers: 130
Conference papers: 79 (click here to view the list)
Articles: 51 (click here to view the list)
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Salak A.N., Cardoso J.P.V., Vieira J.M., Shvartsman V.V., Khalyavin D.D., Fertman E.L., Fedorchenko A.V., Pushkarev A.V., Radyush Y.V., Olekhnovich N.M., Tarasenko R., Feher A., Čižmár E. Magnetic behaviour of perovskite compositions derived from BiFeO3 2021 Magnetochemistry
Vol. 7(11), pp. 151 
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Abstract: The phase content and sequence, the crystal structure, and the magnetic properties of perovskite solid solutions of the (1-y)BiFeO3-yBiZn0.5Ti0.5O3 series (0.05 ≤ y ≤ 0.90) synthesized under high pressure have been studied. Two perovskite phases, namely the rhombohedral R3c and the tetragonal P4mm, which correspond to the structural types of the end members, BiFeO3 and BiZn0.5Ti0.5O3, respectively, were revealed in the as-synthesized samples. The rhombohedral and the tetragonal phases were found to coexist in the compositional range of 0.30 ≤ y ≤ 0.90. Magnetic properties of the BiFe1-y[Zn0.5Ti0.5]yO3 ceramics with y < 0.30 were measured as a function of temperature. The obtained compositional variations of the normalized unit-cell volume and the Néel temperature of the BiFe1-y[Zn0.5Ti0.5]yO3 perovskites in the range of their rhombohedral phase were compared with the respective dependences for the BiFe1-yB3+yO3 perovskites (where B3+ = Ga, Co, Mn, Cr, and Sc). The role of the high-pressure synthesis in the formation of the antiferromagnetic states different from the modulated cycloidal one characteristic of the parent BiFeO3 is discussed.
BibTeX:
@article{salak2021,
  author = {Salak, A. N. and Cardoso, J. P. V. and Vieira, J. M. and Shvartsman, V. V. and Khalyavin, D. D. and Fertman, E. L. and Fedorchenko, A. V. and Pushkarev, A. V. and Radyush, Y. V. and Olekhnovich, N. M. and Tarasenko, R. and Feher, A. and Čižmár, E.},
  title = {Magnetic behaviour of perovskite compositions derived from BiFeO3},
  journal = {Magnetochemistry},
  year = {2021},
  volume = {7},
  number = {11},
  pages = {151},
  doi = {http://dx.doi.org/10.3390/magnetochemistry7110151}
}
Vieira D.E.L., Cardoso J.P.V., Fedorchenko A.V., Fertman E.L., Čižmár E., Feher A., Babkin R.Y., Pashkevich Y.G., Brett C., Vieira J.M., Salak A. Magnetic-field-assisted deposition of self-assembling crystallite layers of Co2+-containing layered double hydroxides 2021 Chemical Communications
Vol. 57, pp. 6899-6902 
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Abstract: Precipitation of nanocrystallites of cobalt-aluminium layered double hydroxides in a magnetic field has been studied. In a magnetic field perpendicular to the substrate, dense and homogeneous films have been obtained. Magnetic anisotropy of the crystallites is explained by deviation from the statistical cation distribution in favour of honeycomb-like coordination of cobalt.
BibTeX:
@article{vieira2021,
  author = {Vieira, D. E. L. and Cardoso, J. P. V. and Fedorchenko, A. V. and Fertman, E. L. and Čižmár, E. and Feher, A. and Babkin, R. Y. and Pashkevich, Y. G. and Brett, C. and Vieira, J. M. and Salak, A.},
  title = {Magnetic-field-assisted deposition of self-assembling crystallite layers of Co2+-containing layered double hydroxides},
  journal = {Chemical Communications},
  publisher = {The Royal Society of Chemistry},
  year = {2021},
  volume = {57},
  pages = {6899-6902},
  doi = {http://dx.doi.org/10.1039/D1CC01599K}
}
Fertman E.L., Fedorchenko A.V., Čižmár E., Vorobiov S., Feher A., Radyush Y.V., Pushkarev A.V., Olekhnovich N.M., Stanulis A., Barron A.R., Khalyavin D.D., Salak A.N. Magnetic diagram of the high-pressure stabilized multiferroic perovskites of the BiFe1-yScyO3 series 2020 Crystals
Vol. 10(10), pp. 950 
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Abstract: Magnetic properties of the high-pressure stabilized perovskite BiFe1-yScyO3 phases (0.1 ≤ y ≤ 0.9) have been studied by means of magnetization measurements and neutron diffraction. The metastable perovskites of this series undergo irreversible polymorphic transformations upon annealing, the phenomenon referred to as conversion polymorphism. It has been found that the solid solutions with y ≥ 0.70 exhibit no long-range magnetic ordering regardless of their polymorph modification, while those with y ≤ 0.60 are all antiferromagnets. Depending on the scandium content, temperature and structural distortions, three types of the antiferromagnetic orderings, involving collinear, canted and cycloidal spin arrangements, have been revealed in the phases obtained via conversion polymorphism and the corresponding magnetic phase diagram has been suggested.
BibTeX:
@article{fertman2020ii,
  author = {Fertman, E. L. and Fedorchenko, A. V. and Čižmár, E. and Vorobiov, S. and Feher, A. and Radyush, Y. V. and Pushkarev, A. V. and Olekhnovich, N. M. and Stanulis, A. and Barron, A. R. and Khalyavin, D. D. and Salak, A. N.},
  title = {Magnetic diagram of the high-pressure stabilized multiferroic perovskites of the BiFe1-yScyO3 series},
  journal = {Crystals},
  year = {2020},
  volume = {10},
  number = {10},
  pages = {950},
  doi = {http://dx.doi.org/10.3390/cryst10100950}
}
Cardoso J.P., Delmonte D., Gilioli E., Fertman E.L., Fedorchenko A.V., Shvartsman V.V., Paukšta V., Grigalaitis R., Banys J., Khalyavin D.D., Vieira J.M., Salak A.N. Phase transitions in the metastable perovskite multiferroics BiCrO3 and BiCr0.9Sc0.1O3: a comparative study 2020 Inorganic Chemistry
Vol. 59(13), pp. 8727-8735 
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Abstract: The temperature behavior of the crystal structure as well as dielectric and magnetic properties of the perovskite bismuth chromate ceramics with the 10 mol % Cr3+-to-Sc3+ substitution were studied and compared with those of the unmodified compound. Using a high-pressure synthesis, BiCrO3 and BiCr0.9Sc0.1O3 were obtained as metastable perovskite phases which are monoclinic C2/c with the √6ap × √2ap × √6ap superstructure (where ap is the primitive perovskite unit-cell parameter) under ambient conditions. At room temperature, the unit cell volume of BiCr0.9Sc0.1O3 is ∼1.3% larger than that of BiCrO3. Both perovskites undergo a reversible structural transition into a nonpolar GdFeO3-type phase (orthorhombic Pnma, √2ap × 2ap × √2ap) in the temperature ranges of 410–420 K (BiCrO3) and 470–520 K (BiCr0.9Sc0.1O3) with a relative jump of the primitive perovskite unit cell volume of about −1.6 and −2.0 respectively. Temperature dependences of the complex dielectric permittivity demonstrate anomalies in the phase transition ranges. The Pnma-to-C2/c crossover in BiCrO3 is accompanied by a decrease in the direct current (dc) conductivity, while in BiCr0.9Sc0.1O3 the conductivity increases. The onset of an antiferromagnetic order in BiCr0.9Sc0.1O3 is observed at the Néel temperature (TN) of about 85 K as compared with TN = 110 K in BiCrO3. In contrast to BiCrO3, which exhibits a spin reorientation at Tsr ∼ 72 K, no such a transition occurs in BiCr0.9Sc0.1O3.
BibTeX:
@article{cardoso2020,
  author = {Cardoso, J. P. and Delmonte, D. and Gilioli, E. and Fertman, E. L. and Fedorchenko, A. V. and Shvartsman, V. V. and Paukšta, V. and Grigalaitis, R. and Banys, J. and Khalyavin, D. D. and Vieira, J. M. and Salak, A. N.},
  title = {Phase transitions in the metastable perovskite multiferroics BiCrO3 and BiCr0.9Sc0.1O3: a comparative study},
  journal = {Inorganic Chemistry},
  year = {2020},
  volume = {59},
  number = {13},
  pages = {8727-8735},
  note = {PMID: 32516538},
  doi = {http://dx.doi.org/10.1021/acs.inorgchem.0c00338}
}
Fertman E.L., Fedorchenko A.V., Desnenko V.A., Shvartsman V.V., Lupascu D.C., Salamon S., Wende H., Vaisburd A.I., Stanulis A., Ramanauskas R., Olekhnovich N.M., Pushkarev A.V., Radyush Y.V., Khalyavin D.D., Salak A.N. Exchange bias effect in bulk multiferroic BiFe0.5Sc0.5O3 2020 AIP Advances
Vol. 10(4), pp. 045102 
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Abstract: Below the Néel temperature, TN∼220 K, at least two nano-scale antiferromagnetic (AFM) phases coexist in the polar polymorph of the BiFe0.5Sc0.5O3 perovskite; one of these phases is a weak ferromagnetic. Non-uniform structure distortions induced by high-pressure synthesis lead to competing AFM orders and a nano-scale spontaneous magnetic phase separated state of the compound. Interface exchange coupling between the AFM domains and the weak ferromagnetic domains causes unidirectional anisotropy of magnetization, resulting in the exchange bias (EB) effect. The EB field, HEB , and the coercive field strongly depend on temperature and the strength of the cooling magnetic field. HEB increases with an increase in the cooling magnetic field and reaches a maximum value of about 1 kOe at 5 K. The exchange field vanishes above TN with the disappearance of long-range magnetic ordering. The effect is promising for applications in electronics as it is large enough and as it is tunable by temperature and the magnetic field applied during cooling.
BibTeX:
@article{fertman2020,
  author = {Fertman, E. L. and Fedorchenko, A. V. and Desnenko, V. A. and Shvartsman, V. V. and Lupascu, D. C. and Salamon, S. and Wende, H. and Vaisburd, A. I. and Stanulis, A. and Ramanauskas, R. and Olekhnovich, N. M. and Pushkarev, A. V. and Radyush, Yu. V. and Khalyavin, D. D. and Salak, A. N.},
  title = {Exchange bias effect in bulk multiferroic BiFe0.5Sc0.5O3},
  journal = {AIP Advances},
  year = {2020},
  volume = {10},
  number = {4},
  pages = {045102},
  doi = {http://dx.doi.org/10.1063/1.5135586}
}
Lukienko I.N., Kharchenko M.F., Fedorchenko A.V., Kharlan I.A., Tutakina O.P., Stetsenko O.N., Neves C.S., Salak A.N. Faraday effect and fragmentation of ferromagnetic layers in multilayer Co/Cu(1 1 1) nanofilms 2020 Journal of Magnetism and Magnetic Materials
Vol. 505, pp. 166706 
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Abstract: With purpose to investigate influence of magnetically non-active metal layers on the Faraday effect in multilayer Ferromagnetic/Normal metal films, dependences of the Faraday rotation angles of the light polarization plane on magnetic field have been studied in multilayer [Co/Cu] nanofilms. It was revealed that the Faraday rotation φ varies with thickness of the Cu layers dCu. This φ(dCu) dependence consists of the monotonic component, namely a gradual rise of the angle with increase of dCu, and the non-monotonic one represented by two minima. The monotonic changes of the Faraday rotation were satisfactory described in frames of the effective medium method. Two minima are explained with the Co layer’s fragmentation due to influence of size electron quantization in the Cu layers on formation of Co clusters during deposition of the films.
BibTeX:
@article{lukienko2020,
  author = {Lukienko, I. N. and Kharchenko, M. F. and Fedorchenko, A. V. and Kharlan, I. A. and Tutakina, O. P. and Stetsenko, O. N. and Neves, C. S. and Salak, A. N.},
  title = {Faraday effect and fragmentation of ferromagnetic layers in multilayer Co/Cu(1 1 1) nanofilms},
  journal = {Journal of Magnetism and Magnetic Materials},
  year = {2020},
  volume = {505},
  pages = {166706},
  doi = {https://doi.org/10.1016/j.jmmm.2020.166706}
}
Salak A.N., Vieira D.E.L., Lukienko I.M., Shapovalov Y.O., Fedorchenko A.V., Fertman E.L., Pashkevich Y.G., Babkin R.Y., Shilin A.D., Rubanik V.V., Ferreira M.G.S., Vieira J.M. High-power ultrasonic synthesis and magnetic-field-assisted arrangement of nanosized crystallites of cobalt-containing layered double hydroxides 2019 ChemEngineering
Vol. 3(3), pp. 62 
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Abstract: High-quality stoichiometric Co2Al-NO3 and Co2Al-CO3 layered double hydroxides (LDHs) have been obtained by precipitation followed by anion exchange, both high-power-sonication assisted. Application of high-power ultrasound has been demonstrated to result in a considerable acceleration of the crystallization process and the anion-exchange reaction. Two independent approaches were used to form bulk and 2-D samples of Co2Al-NO3 with the oriented crystallites, namely uniaxial pressing of deposits from sonicated LDH slurries and magnetic field-assisted arrangement of LDH crystallites precipitating on glass substrates. A convenient way of preparation of semi-transparent compacts with relatively big blocks of oriented crystallites have been demonstrated. Thin dense transparent films of highly-ordered crystallites of Co2Al-NO3 LDH have been produced and characterized.
BibTeX:
@article{salak2019,
  author = {Salak, A. N. and Vieira, D. E. L. and Lukienko, I. M. and Shapovalov, Y. O. and Fedorchenko, A. V. and Fertman, E. L. and Pashkevich, Y. G. and Babkin, R. Yu. and Shilin, A. D. and Rubanik, V. V. and Ferreira, M. G. S. and Vieira, J. M.},
  title = {High-power ultrasonic synthesis and magnetic-field-assisted arrangement of nanosized crystallites of cobalt-containing layered double hydroxides},
  journal = {ChemEngineering},
  year = {2019},
  volume = {3},
  number = {3},
  pages = {62},
  note = {https://www.mdpi.com/2305-7084/3/3/62},
  doi = {http://dx.doi.org/10.3390/chemengineering3030062}
}
Khalyavin D.D., Salak A.N., Fertman E.L., Kotlyar O.V., Eardley E., Olekhnovich N.M., Pushkarev A.V., Radyush Y.V., Fedorchenko A.V., Desnenko V.A., Manuel P., Ding L., Čižmár E., Feher A. The phenomenon of conversion polymorphism in Bi-containing metastable perovskites 2019 Chemical Communications
Vol. 55, pp. 4683-4686 
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Abstract: A post-synthesis thermal treatment of metastable phases in the high-pressure stabilised perovskite BiFe1-yScyO3 system results in the irreversible formation of polymorphs which represent novel polar and antipolar structures with interesting magnetic properties. Such annealing-stimulated polymorphism is believed to be a general phenomenon which can be found in other systems.
BibTeX:
@article{khalyavin2019,
  author = {Khalyavin, D. D. and Salak, A. N. and Fertman, E. L. and Kotlyar, O. V. and Eardley, E. and Olekhnovich, N. M. and Pushkarev, A. V. and Radyush, Y. V. and Fedorchenko, A. V. and Desnenko, V. A. and Manuel, P. and Ding, L. and Čižmár, E. and Feher, A.},
  title = {The phenomenon of conversion polymorphism in Bi-containing metastable perovskites},
  journal = {Chemical Communications},
  publisher = {The Royal Society of Chemistry},
  year = {2019},
  volume = {55},
  pages = {4683-4686},
  doi = {http://dx.doi.org/10.1039/C9CC00472F}
}
Babkin R.Y., Pashkevich Y.G., Fedorchenko A.V., Fertman E.L., Desnenko V.A., Prokhvatilov A.I., Galtsov N.N., Vieira D.E.L., Salak A.N. Impact of temperature dependent octahedra distortions on magnetic properties of Co-containing double layered hydroxides 2019 Journal of Magnetism and Magnetic Materials
Vol. 473, pp. 501-504 
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Abstract: Distortions of hydroxide octahedral complexes in the CoIInAlIII layered double hydroxides (LDHs) (n = CoII/AlIII = 2 and 3) were studied as a function of the ratio of divalent-to-trivalent cations and temperature. A method for calculation the magnetic susceptibility of polycrystalline samples taking into account the statistical distribution of divalent and trivalent cations, and their effect on the distortions of the original structure is proposed. It is shown that the presence of a local maximum on the magnetic susceptibility curve of ConAl LDHs compounds near T ∼ 160 K is due to freezing of the lattice parameters and, as a consequence, freezing of the tilting fluctuations of the O-H bonds.
BibTeX:
@article{babkin2019,
  author = {Babkin, R. Y. and Pashkevich, Y. G. and Fedorchenko, A. V. and Fertman, E. L. and Desnenko, V. A. and Prokhvatilov, A. I. and Galtsov, N. N. and Vieira, D. E. L. and Salak, A. N.},
  title = {Impact of temperature dependent octahedra distortions on magnetic properties of Co-containing double layered hydroxides},
  journal = {Journal of Magnetism and Magnetic Materials},
  year = {2019},
  volume = {473},
  pages = {501-504},
  doi = {http://dx.doi.org/10.1016/j.jmmm.2018.10.077}
}
Desnenko V.A., Sirenko V.A., Troyanchuk I.O., Fedorchenko A.V., Yeremenko A.V. Low-temperature relaxation of magnetization in manganite Pr0.4Bi0.3Ca0.3MnO3 2018 Low Temperature Physics
Vol. 44(9), pp. 962-965 
DOI   PDF  
Abstract: Low-temperature relaxation of magnetization in Pr0.4Bi0.3Ca0.3MnO3 ceramics was measured after cooling in a magnetic field and aging at temperatures from 5 K to 38 K near the transition temperature to the magnetically ordered state. It was found that the relaxation process has a thermoactivation character at the first stage and is described in terms of the Arrhenius equation. Its activation energy Q ≈ 1.1 meV is comparable with the antiferromagnetic interaction energy in this compound. The temperature–time dependence of the relaxation rate at the second stage is described by a power law. The relaxation slows down as the temperature approaches the critical value, which may be associated with the formation of a cluster structure in the studied compound under these conditions.
BibTeX:
@article{desnenko2018,
  author = {Desnenko, V. A. and Sirenko, V. A. and Troyanchuk, I. O. and Fedorchenko, A. V. and Yeremenko, A. V.},
  title = {Low-temperature relaxation of magnetization in manganite Pr0.4Bi0.3Ca0.3MnO3},
  journal = {Low Temperature Physics},
  year = {2018},
  volume = {44},
  number = {9},
  pages = {962-965},
  doi = {http://dx.doi.org/10.1063/1.5052685}
}
Čižmár E., Šoltésová D., Kazheva O.N., Alexandrov G.G., Kravchenko A.V., Chekulaeva L.A., Kosenko I.D., Sivaev I.B., Bregadze V.I., Fedorchenko A.V., Starodub V.A., Buravov L.I., Dyachenko O.A., Feher A. Large magnetic anisotropy of chromium(III) ions in a bis(ethylenedithio)tetrathiafulvalenium salt of chromium bis(dicarbollide), (ET)2[3,3′-Cr(1,2-C2B9H11)2] 2018 Transition Metal Chemistry
Vol. 43(7), pp. 647-655 
DOI   PDF  
Abstract: The synthesis of a radical-cation salt based on a derivative of tetrathiafulvalene, (ET)2[3,3′-Cr(1,2-C2B9H11)2] (ET = bis(ethylenedithio)tetrathiafulvalenium), was accomplished by electrochemical anodic oxidation of ET in the presence of (Me4N)[3,3´-Cr(1,2-C2B9H11)2] in the galvanostatic regime. An electric conductivity σ (293 K) = 7 × 10−3 Ohm−1 cm−1 with semiconductor activation energy Ea ≅ 0.1 eV in the range of 127–300 K was observed. The crystal structure of (ET)2[3,3′-Cr(1,2-C2B9H11)2] was determined by X-ray diffraction at 173 K, revealing the presence of structural tetramers in radical-cation stacks. The magnetic properties of the complex were investigated in the temperature range 1.8–300 K using magnetometry and EPR, showing that the magnetic structure of (ET)2[3,3′-Cr(1,2-C2B9H11)2] consists of two independent magnetic subsystems. Cation radicals form a rectangular magnetic lattice in the ab-plane with significant antiferromagnetic exchange interactions. The chromium bis(dicarbollide) anions are characterized by unusually strong positive zero-field splitting of the Cr(III) ions, which was confirmed by ab initio calculations.
BibTeX:
@article{cizmar2018,
  author = {Čižmár, E. and Šoltésová, D. and Kazheva, O. N. and Alexandrov, G. G. and Kravchenko, A. V. and Chekulaeva, L. A. and Kosenko, I. D. and Sivaev, I. B. and Bregadze, V. I. and Fedorchenko, A. V. and Starodub, V. A. and Buravov, L. I. and Dyachenko, O. A. and Feher, A.},
  title = {Large magnetic anisotropy of chromium(III) ions in a bis(ethylenedithio)tetrathiafulvalenium salt of chromium bis(dicarbollide), (ET)2[3,3′-Cr(1,2-C2B9H11)2]},
  journal = {Transition Metal Chemistry},
  year = {2018},
  volume = {43},
  number = {7},
  pages = {647-655},
  doi = {http://dx.doi.org/10.1007/s11243-018-0253-1}
}
Fedorchenko A.V., Fertman E.L., Salak A.N., Desnenko V.A., Čižmár E., Feher A., Vaisburd A.I., Olekhnovich N.M., Pushkarev A.V., Radyush Y.V., Zarkov A., Kareiva A. Unusual magnetic properties of the polar orthorhombic BiFe0.5Sc0.5O3 perovskite 2018 Journal of Magnetism and Magnetic Materials
Vol. 465, pp. 328-332 
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Abstract: Magnetic properties of new multiferroic BiFe0.5Sc0.5O3 perovskite which exists in two different orthorhombic polymorphs, the antipolar Pnma and the polar Ima2, were studied using a SQUID-magnetometer technique in magnetic fields up to 50 kOe in the temperature range of 5-300 K. Both polymorphs show a weak ferromagnetic component below the Néel temperature, TN ~220 K. A wide cusp-like anomaly of the temperature dependent magnetic susceptibility was revealed below 200 K. The anomaly is dependent on the magnetic field applied and can be associated with the glassy magnetic behavior of the compound. The best fit of the initial magnetization curves taken at each temperature can be obtained as a sum of two contributions, namely the nonlinear in field and the linear one. The nonlinear contribution appeared to be temperature and magnetic field dependent, which is in a good agreement with the magnetization experimentally obtained as a function of temperature in different magnetic fields applied. Increase of external magnetic field leads to a decrease of the nonlinear contribution to the total magnetic moment.
BibTeX:
@article{fedorchenko2018,
  author = {Fedorchenko, A. V. and Fertman, E. L. and Salak, A. N. and Desnenko, V. A. and Čižmár, E. and Feher, A. and Vaisburd, A. I. and Olekhnovich, N. M. and Pushkarev, A. V. and Radyush, Yu. V. and Zarkov, A. and Kareiva, A.},
  title = {Unusual magnetic properties of the polar orthorhombic BiFe0.5Sc0.5O3 perovskite},
  journal = {Journal of Magnetism and Magnetic Materials},
  year = {2018},
  volume = {465},
  pages = {328-332},
  doi = {http://dx.doi.org/10.1016/j.jmmm.2018.06.015}
}
Šoltésová D., Vasylets G., Čižmár E., Fedorchenko A.V., Starodub V., Medviediev V., Shishkin O., Bukrynov O., Feher A. Magnetic properties of the anion-radical salts [M(bipy)3](TCNQ)4·X, where M = Co, Ni, Zn and X = H2O or (CH3)2CO 2018 Inorganica Chimica Acta
Vol. 471, pp. 272-279 
DOI   PDF  
Abstract: An anion-radical salt (ARS) [Co(bipy)3](TCNQ)4·H2O was synthesized and its crystal structure was resolved. The experimental investigation of [Co(bipy)3](TCNQ)4·H2O and two ARS with similar crystal structure [Zn(bipy)3](TCNQ)4·H2O and [Ni(bipy)3](TCNQ)4·(CH3)2CO by the measurement of the temperature dependence of magnetic susceptibility at temperature from 1.8 K to 300 K, the field dependence of magnetization up to 7 T at different temperatures and EPR spectra in temperature range from 2 K to 300 K was performed. [Zn(bipy)3](TCNQ)4·H2O was used to estimate the contribution of the TCNQ radicals to the magnetic moment. In result, the compound [Co(bipy)3](TCNQ)4·H2O was characterized by the presence of Co2+ ions in spin-admixed state and low-temperature susceptibility, magnetization and specific heat of [Ni(bipy)3](TCNQ)4·(CH3)2CO was shown to be dominated by the contribution of single-ion anisotropy of Ni2+ ions.
BibTeX:
@article{soltesova2018,
  author = {Šoltésová, D. and Vasylets, G. and Čižmár, E. and Fedorchenko, A. V. and Starodub, V. and Medviediev, V. and Shishkin, O. and Bukrynov, O. and Feher, A.},
  title = {Magnetic properties of the anion-radical salts [M(bipy)3](TCNQ)4·X, where M = Co, Ni, Zn and X = H2O or (CH3)2CO},
  journal = {Inorganica Chimica Acta},
  year = {2018},
  volume = {471},
  pages = {272-279},
  doi = {http://dx.doi.org/10.1016/j.ica.2017.11.001}
}
Vieira D.E.L., Salak A.N., Fedorchenko A.V., Pashkevich Y.G., Fertman E.L., Desnenko V.A., Babkin R.Y., Čižmár E., Feher A., Lopes A.B., Ferreira M.G.S. Magnetic phenomena in Co-containing layered double hydroxides 2017 Low Temperature Physics
Vol. 43(8), pp. 977-981 
DOI   PDF  
Abstract: Magnetic behavior of CoII(n)AlIII layered double hydroxides (LDHs) (n = Co/Al = 2 and 3) intercalated with nitrate was studied as a function of temperature. Both LDH compounds are paramagnetic above about 8 K. A rapid increase of their magnetic moments occurs below this temperature until the moments reach the maximum values at Tmax of 4.0 K and 3.2 K for Co(2)Al–NO3 and Co(3)Al–NO3, respectively. Below Tmax, the zero-field-cooled and the field-cooled static magnetization curves are strongly different. Along with this low-temperature phenomena, Co(2)Al–NO3 and Co(3)Al–NO3 demonstrate anomalous behavior of their temperature dependence magnetic susceptibility in a higher-temperature range: between 75 and 175 K, both the paramagnetic Curie temperature and the effective magnetic moment change in a non-monotonous way. Possible structural reasons of the observed magnetic behavior of the CoII(n)AlIII LDHs are discussed.
BibTeX:
@article{vieira2017,
  author = {Vieira, D. E. L. and Salak, A. N. and Fedorchenko, A. V. and Pashkevich, Y. G. and Fertman, E. L. and Desnenko, V. A. and Babkin, R. Y. and Čižmár, E. and Feher, A. and Lopes, A. B. and Ferreira, M. G. S.},
  title = {Magnetic phenomena in Co-containing layered double hydroxides},
  journal = {Low Temperature Physics},
  year = {2017},
  volume = {43},
  number = {8},
  pages = {977-981},
  doi = {http://dx.doi.org/10.1063/1.5001299}
}
Fedorchenko A.V., Fertman E.L., Desnenko V.A., Kotlyar O.V., Čižmár E., Shvartsman V.V., Lupascu D.C., Salamon S., Wende H., Salak A.N., Khalyavin D.D., Olekhnovich N.M., Pushkarev A.V., Radyush Y., Feher A. Magnetic properties of the Bi0.65La0.35Fe0.5Sc0.5O3 perovskite 2017 Acta Physica Polonica A
Vol. 131(4), pp. 1069-1071 
DOI   PDF  
Abstract: Magnetic properties of polycrystalline multiferroic Bi0.65La0.35Fe0.5Sc0.5O3 synthesized under high-pressure (6 GPa) and high-temperature (1500 K) conditions were studied using a SQUID magnetometer technique. The temperature dependent static magnetic moment M was measured in both zero-field-cooled and field-cooled modes over the temperature range of 5-300 K in low magnetic field H=0.02 kOe. The field dependent magnetization M(H) was measured in magnetic fields up to 50 kOe at different temperatures up to 230 K after zero-field cooling procedure. A long-range magnetic ordering of the antiferromagnetic type with a weak ferromagnetic contribution takes place below TN ≈ 220 K. Magnetic hysteresis loops taken below TN show a huge coercive field up to Hc ≈10 kOe, while the magnetic moment does not saturate up to 50 kOe. A strong effect of magnetic field on the magnetic properties of the compound has been found. Below TN ≈220 K the derivatives of the initial magnetization curves demonstrate the existence of a temperature-dependent anomaly in fields of H=15÷25 kOe. The nature of the anomaly is unknown and requires additional study.
BibTeX:
@article{fedorchenko2017,
  author = {Fedorchenko, A. V. and Fertman, E. L. and Desnenko, V. A. and Kotlyar, O. V. and Čižmár, E. and Shvartsman, V. V. and Lupascu, D. C. and Salamon, S. and Wende, H. and Salak, A. N. and Khalyavin, D. D. and Olekhnovich, N. M. and Pushkarev, A. V. and Yu.V. Radyush and Feher, A.},
  title = {Magnetic properties of the Bi0.65La0.35Fe0.5Sc0.5O3 perovskite},
  journal = {Acta Physica Polonica A},
  year = {2017},
  volume = {131},
  number = {4},
  pages = {1069-1071},
  doi = {http://dx.doi.org/10.12693/APhysPolA.131.1069}
}
Fertman E.L., Fedorchenko A.V., Khalyavin D.D., Salak A.N., Baran A., Desnenko V.A., Kotlyar O.V., Čižmár E., Feher A., Syrkin E.S., Vaisburd A.I., Olekhnovich N.M., Pushkarev A.V., Radyush Y.V., Stanulis A., Kareiva A. Multiferroic Bi0.65La0.35Fe0.5Sc0.5O3 perovskite: Magnetic and thermodynamic properties 2017 Journal of Magnetism and Magnetic Materials
Vol. 429, pp. 177-181 
DOI   PDF  
Abstract: Magnetic and thermodynamic properties of polycrystalline multiferroic Bi0.65La0.35Fe0.5Sc0.5O3 synthesized under high-pressure and high-temperature conditions are reported. Magnetic properties were studied using a SQUID magnetometer technique over the temperature range of 5-300 K in magnetic fields up to H=10 kOe. The field dependent magnetization M(H) was measured in magnetic fields up to 50 kOe at different temperatures up to 230 K after zero-field cooling procedure. A long-range magnetic ordering of the AFM type with a weak FM contribution occurs below the Néel temperature TN ~237 K. Magnetic hysteresis loops taken below TN show a huge coercive field up to Hc ~10 kOe. A strong effect of magnetic field on the magnetic properties of the compound has been found. Derivative of the initial magnetization curves demonstrates a temperature-dependent anomaly in fields of H=15−25 kOe. Besides, an anomaly of the temperature dependent zero-field cooled magnetization measured in magnetic fields of 6-7 kOe has been found. Origin of both anomalies is associated with inhomogeneous magnetic state of the compound. The heat capacity has been measured from 2 K up to room temperature and a significant contribution from the magnon excitations at low temperatures has been detected. From the low-temperature heat capacity, an anisotropy gap of the magnon modes of the order 3.7 meV and Debye temperature TD=189 K have been determined.
BibTeX:
@article{fertman2017,
  author = {Fertman, E. L. and Fedorchenko, A. V. and Khalyavin, D. D. and Salak, A. N. and Baran, A. and Desnenko, V. A. and Kotlyar, O. V. and Čižmár, E. and Feher, A. and Syrkin, E. S. and Vaisburd, A. I. and Olekhnovich, N. M. and Pushkarev, A. V. and Radyush, Yu. V. and Stanulis, A. and Kareiva, A.},
  title = {Multiferroic Bi0.65La0.35Fe0.5Sc0.5O3 perovskite: Magnetic and thermodynamic properties},
  journal = {Journal of Magnetism and Magnetic Materials},
  year = {2017},
  volume = {429},
  pages = {177-181},
  doi = {http://dx.doi.org/10.1016/j.jmmm.2017.01.037}
}
Zhuravleva I.P., Grechnev G.E., Panfilov A.S., Lyogenkaya A.A., Kotlyar O.V., Fedorchenko A.V., Feher A. Electronic structure and magnetic properties of RT4Al8 (R = Sc, Y, La, Lu; T = Fe, Mn, Cr) compounds. Hydrostatic pressure effects 2016 Low Temperature Physics
Vol. 42(6), pp. 458-465 
DOI   PDF  
Abstract: We present results of theoretical and experimental studies of the electronic structure and magnetic properties of RFe4Al8, RMn4Al8, and RCr4Al8 compounds with nonmagnetic elements R = Sc, Y, La, and Lu. The electron spectrum and field induced magnetic moment, as well as their dependences on the unit cell volume, are calculated for the paramagnetic phase of the RT4Al8 systems. The calculations are supplemented by measurements of the magnetic susceptibility of representative RT4Al8 compounds as a function of temperature and hydrostatic pressure.
BibTeX:
@article{zhuravleva2016,
  author = {Zhuravleva, I. P. and Grechnev, G. E. and Panfilov, A. S. and Lyogenkaya, A. A. and Kotlyar, O. V. and Fedorchenko, A. V. and Feher, A.},
  title = {Electronic structure and magnetic properties of RT4Al8 (R = Sc, Y, La, Lu; T = Fe, Mn, Cr) compounds. Hydrostatic pressure effects},
  journal = {Low Temperature Physics},
  year = {2016},
  volume = {42},
  number = {6},
  pages = {458-465},
  doi = {http://dx.doi.org/10.1063/1.4954784}
}
Khalyavin D.D., Salak A.N., Lopes A.B., Olekhnovich N.M., Pushkarev A.V., Radyush Y.V., Fertman E.L., Desnenko V.A., Fedorchenko A.V., Manuel P., Feher A., Vieira J.M., Ferreira M.G.S. Magnetic structure of an incommensurate phase of La-doped BiFe0.5Sc0.5O3: Role of antisymmetric exchange interactions 2015 Physical Review B
Vol. 92(22), pp. 224428 
DOI   PDF  
Abstract: A 20% substitution of Bi with La in the perovskite Bi1−x Lax Fe0.5 Sc0.5 O3 system obtained under high-pressure and high-temperature conditions has been found to induce an incommensurately modulated structural phase. The room-temperature x-ray and neutron powder diffraction patterns of this phase were successfully refined using the I mma(0,0,γ )s00 superspace group (γ = 0.534(3)) with the modulation applied to Bi/La and oxygen displacements. The modulated structure is closely related to the prototype antiferroelectric structure of PbZrO3 which can be considered as the lock-in variant of the latter with γ = 0.5. Below TN ∼ 220 K, the neutron diffraction data provide evidence for a long-range G-type antiferromagnetic ordering commensurate with the average I mma structure. Based on a general symmetry consideration, we show that the direction of the spins is controlled by the antisymmetric exchange imposed by the two primary structural distortions, namely oxygen octahedral tilting and incommensurate atomic displacements. The tilting is responsible for the onset of a weak ferromagnetism, observed in magnetization measurements, whereas the incommensurate displacive mode is dictated by the symmetry to couple a spin-density wave. The obtained results demonstrate that antisymmetric exchange is the dominant anisotropic interaction in Fe3+-based distorted perovskites with a nearly quenched orbital degree of freedom.
BibTeX:
@article{khalyavin2015ii,
  author = {Khalyavin, D. D. and Salak, A. N. and Lopes, A. B. and Olekhnovich, N. M. and Pushkarev, A. V. and Radyush, Yu. V. and Fertman, E. L. and Desnenko, V. A. and Fedorchenko, A. V. and Manuel, P. and Feher, A. and Vieira, J. M. and Ferreira, M. G. S.},
  title = {Magnetic structure of an incommensurate phase of La-doped BiFe0.5Sc0.5O3: Role of antisymmetric exchange interactions},
  journal = {Physical Review B},
  year = {2015},
  volume = {92},
  number = {22},
  pages = {224428},
  doi = {http://dx.doi.org/10.1103/PhysRevB.92.224428}
}
Fertman E.L., Fedorchenko A.V., Kotlyar A.V., Desnenko V.A., Čižmár E., Baran A., Khalyavin D.D., Salak A.N., Shvartsman V.V., Feher A. Exchange bias phenomenon in
(Nd1-xYx)2/3Ca1/3MnO3 (x = 0, 0.1) perovskites
2015 Low Temperature Physics
Vol. 41(12), pp. 1001-1005 
DOI   PDF  
Abstract: Exchange bias phenomenon, evident of antiferromagnetic-ferromagnetic phase segregation state, has been observed in (Nd1 xYx)2/3Ca1/3MnO 3 (x 1⁄4 0, 0.1) compounds at low temperatures. A contribution to the total magnetization of the compounds due to the ferromagnetic phase has been evaluated. It has been found that yttrium doping leads to the growth of the ferromagnetic phase fraction. The ferromagnetic phase in the doped compound has a lower coercivity Hc and more rectangular form of the hysteresis loop. The values of the exchange bias field HEB and coercivity are found to be strongly dependent on the cooling magnetic field Hcool. In sufficiently high magnetic fields, Hcool > 5 kOe, HEB in the doped compound is about twice as low as in the parent compound. This difference is attributed to a lower exchange interaction and higher saturation magnetization of the ferromagnetic phase in (Nd0.9Y0.1)2/3Ca1/3MnO3.
BibTeX:
@article{fertman2015ii,
  author = {Fertman, E. L. and Fedorchenko, A. V. and Kotlyar, A. V. and Desnenko, V. A. and Čižmár, E. and Baran, A. and Khalyavin, D. D. and Salak, A. N. and Shvartsman, V. V. and Feher, A.},
  title = {Exchange bias phenomenon in 
(Nd1-xYx)2/3Ca1/3MnO3 (x = 0, 0.1) perovskites}, journal = {Low Temperature Physics}, year = {2015}, volume = {41}, number = {12}, pages = {1001-1005}, doi = {http://dx.doi.org/10.1063/1.4936671} }
Khalyavin D., Salak A.N., Manuel P., Olekhnovich N.M., Pushkarev A.V., Radysh Y.V., Fedorchenko A.V., Fertman E.L., Desnenko V.A., Ferreira M.G.S. Antisymmetric exchange in La-substituted BiFe0.5Sc0.5O3 system: symmetry adapted distortion modes approach 2015 Zeitschrift für Kristallographie - Crystalline Materials
Vol. 230(12), pp. 767-774 
DOI   PDF  
Abstract: Neutron powder diffraction measurements on the 35 % La-substituted Bi1−xLaxFe0.5Sc0.5O3 composition revealed that the samples obtained under high-pressure (6 GPa) and high-temperature (1500 K) conditions crystalize into a distorted perovskite structure with the orthorhombic Pnma symmetry and the unit cell parameters: ao = 5.6745(2) Å, bo = 7.9834(3) Å and co = 5.6310(2) Å. A long-range magnetic ordering takes place below 220 K and implies a G-type magnetic structure with the moments 4.10(4)μB per Fe aligned predominately along the orthorhombic c-axis. The space group representation theory using the orthorhombic symmetry yields four bi-linear coupling schemes for the magnetic order parameters imposed by antisymmetric exchange interactions. The couplings are analysed based on symmetry adapted distortion modes defined in respect of the undistorted cubic perovskite structure. The approach allows a quantitative estimation of the coupling strength. It is shown that the experimentally found spin configuration combines the magnetic order parameters coupled by the atomic displacement modes with the largest amplitudes. The results indicate that the antisymmetric exchange is the dominant anisotropic term which fully controls the direction of the Fe3+ spins in the distorted perovskite lattice.
BibTeX:
@article{khalyavin2015,
  author = {Khalyavin, D. and Salak, A. N. and Manuel, P. and Olekhnovich, N. M. and Pushkarev, A. V. and Radysh, Yu. V. and Fedorchenko, A. V. and Fertman, E. L. and Desnenko, V. A. and Ferreira, M. G. S.},
  title = {Antisymmetric exchange in La-substituted BiFe0.5Sc0.5O3 system: symmetry adapted distortion modes approach},
  journal = {Zeitschrift für Kristallographie - Crystalline Materials},
  year = {2015},
  volume = {230},
  number = {12},
  pages = {767-774},
  doi = {http://dx.doi.org/10.1515/zkri-2015-1873}
}
Panfilov A.S., Grechnev G.E., Fedorchenko A.V., Conder K., Pomjakushina E.V. Magnetic properties of Mn-doped Bi2Se3 compound: temperature dependence and pressure effects 2015 Journal of Physics: Condensed Matter
Vol. 27(45), pp. 456002 
DOI   PDF  
Abstract: Magnetic susceptibility χ of Bi[2-x]Mn[x]Se[3] (x = 0.01-0.2) was measured in the temperature range 4.2-300 K. For all the samples, a Curie-Weiss behaviour of χ(T) was revealed with effective magnetic moments of Mn ions corresponding to the spin value S=5/2, which couple antiferromagnetically with the paramagnetic Curie temperature Θ ~ -50 K. In addition, for the samples of nominal composition x = 0.1 and 0.2 the effect of a hydrostatic pressure P up to 2 kbar on χ has been measured at fixed temperatures 78 and 300 K that allowed to estimate the pressure derivative of Θ to be dΘ/dP ~ -0.8 K/kbar. Based on the observed behaviour of Θ with varied Mn concentration and pressure, a possible mechanism of interaction between localized Mn moments is discussed.
BibTeX:
@article{panfilov2015ii,
  author = {Panfilov, A. S. and Grechnev, G. E. and Fedorchenko, A. V. and Conder, K. and Pomjakushina, E. V.},
  title = {Magnetic properties of Mn-doped Bi2Se3 compound: temperature dependence and pressure effects},
  journal = {Journal of Physics: Condensed Matter},
  year = {2015},
  volume = {27},
  number = {45},
  pages = {456002},
  doi = {http://dx.doi.org/10.1088/0953-8984/27/45/456002}
}
Arhipov P., Tkachenko S., Gerasymov I., Sidletskiy O., Hubenko K., Vasyukov S., Shiran N., Baumer V., Mateychenko P., Fedorchenko A., Zorenko Y., Zhydachevskii Y., Lebbou K., Korjik M. Growth and characterization of large CeAlO3 perovskite crystals 2015 Journal of Crystal Growth
Vol. 430, pp. 116-121 
DOI   PDF  
Abstract: This study is focused on obtaining large CeAlO3 single crystals. Using Czochralski and Edge-Defined Film Fed Growth techniques, crystals of length up to 130 mm were obtained. The crystals belong to the tetragonal low temperature modification of CeAlO3, space group P4/mmm, a=3.7669 Å, с=3.7967 Å. Density and crystallographic parameters as well as some optical, luminescence and magnetic properties of CeAlO3 were studied. The crystals demonstrate rather bright luminescence under UV-excitation, while no luminescence has been registered under X-rays. Ceramic and single crystalline CeAlO3 samples demonstrate p-type conductivity and promising paramagnetic properties.
BibTeX:
@article{arhipov2015,
  author = {Arhipov, P. and Tkachenko, S. and Gerasymov, Ia. and Sidletskiy, O. and Hubenko, K. and Vasyukov, S. and Shiran, N. and Baumer, V. and Mateychenko, P. and Fedorchenko, A. and Zorenko, Yu. and Zhydachevskii, Ya. and Lebbou, K. and Korjik, M.},
  title = {Growth and characterization of large CeAlO3 perovskite crystals},
  journal = {Journal of Crystal Growth},
  year = {2015},
  volume = {430},
  pages = {116-121},
  doi = {http://dx.doi.org/10.1016/j.jcrysgro.2015.08.025}
}
Fertman E., Syrkin E., Lykah V., Desnenko V., Beznosov A., Pal-Val P., Pal-Val L., Fedorchenko A., Khalyavin D., Feher A. Structural phase transition in La2/3Ba1/3MnO3 perovskite: Elastic, magnetic, and lattice anomaliesand microscopic mechanism 2015 AIP Advances
Vol. 5(7), pp. 077189 
DOI   PDF  
Abstract: The temperature dependences of the elastic and magnetic properties of polycrystalline perovskite manganite La2/3Ba1/3MnO3 were studied using ultrasonic and SQUID magnetometer techniques. The minimum of the temperature-dependent sound velocity v(T) and corresponding maximum of the decrement δ(T) were found in the vicinity of the structural phase transition R3̄ c↔Imma at Ts ∼ 200 K. Large alterations of v and δ indicate a structural phase transition of the soft mode type. A high sensitivity of dc magnetization to a low uniaxial pressure caused by the softening was found in the Ts region. A negative value of the linear thermal expansion coefficient along one of the crystallographic axis was found in the Imma phase near Ts . The proposed microscopic mechanism explains the appearance of the soft mode in the vicinity of the structural phase transition temperature associated with the displacement of the manganese atom from the center of the oxygen octahedron.
BibTeX:
@article{fertman2015,
  author = {Fertman, E. and Syrkin, E. and Lykah, V. and Desnenko, V. and Beznosov, A. and Pal-Val, P. and Pal-Val, L. and Fedorchenko, A. and Khalyavin, D. and Feher, A.},
  title = {Structural phase transition in La2/3Ba1/3MnO3 perovskite: Elastic, magnetic, and lattice anomaliesand microscopic mechanism},
  journal = {AIP Advances},
  year = {2015},
  volume = {5},
  number = {7},
  pages = {077189},
  doi = {http://dx.doi.org/10.1063/1.4928075}
}
Panfilov A.S., Grechnev G.E., Zhuravleva I.P., Fedorchenko A.V., Muratov V.B. Specific features of the magnetic properties of RB4 (R = Ce, Sm and Yb) tetraborides. Effects of pressure 2015 Low Temperature Physics
Vol. 41(3), pp. 193-198 
DOI   PDF  
Abstract: The temperature dependence and the effect of pressure P up to 2 kbar on the magnetic susceptibility χ of the tetraborides SmB4 and YbB4 was studied. For the compound CeB4, the electronic structure and magnetic susceptibility were calculated from first principles as a function of the atomic volume. The results show that in the studied tetraborides, rare-earth ions (Ce 4+, Sm3+ and Yb2.8+) exhibit different valence states, which determines the specific features of their magnetic properties. In particular, the obtained pressure derivatives of susceptibility dlnv/dP for cerium, samarium and 1ytterbium tetraborides are -2, -0.6 and +2.7 (in units of Mbar ), respectively, which are characteristic for the exchange-enhanced itinerant paramagnetism, Van Vleck ionic paramagnetism with a stable f-shell, and the magnetism of rare-earth ions in the intermediate valence state.
BibTeX:
@article{panfilov2015,
  author = {Panfilov, A. S. and Grechnev, G. E. and Zhuravleva, I. P. and Fedorchenko, A. V. and Muratov, V. B.},
  title = {Specific features of the magnetic properties of RB4 (R = Ce, Sm and Yb) tetraborides. Effects of pressure},
  journal = {Low Temperature Physics},
  year = {2015},
  volume = {41},
  number = {3},
  pages = {193-198},
  doi = {http://dx.doi.org/10.1063/1.4916067}
}
Grechnev G.E., Panfilov A.S., Fedorchenko A.V., Lyogenkaya A.A., Zhuravleva I.P., Chareev D.A., Nekrasov A.N., Mitrofanova E.S., Volkova O.S., Vasiliev A.N., Eriksson O. Anisotropy of magnetic properties of Fe1+yTe 2014 Journal of Physics: Condensed Matter
Vol. 26(43), pp. 436003 
DOI   PDF  
Abstract: The magnetic properties of Fe1+yTe single crystals (y≃0.1-0.18) were studied at temperatures 4.2-300K. At an ambient pressure, with decreasing temperature a drastic drop in χ(T) was confirmed at T≃ 60-65K, which appears to be closely related to the antiferromagnetic (AFM) ordering. It is found that the magnitudes of the anisotropy of magnetic susceptibility Δχ in the AFM phase are close in the studied samples, whereas the sign of the anisotropy apparently depends on the small variations of the excess iron y in Fe1+yTe samples. The performed DFT calculations of the electronic structure and magnetic properties for the stoichiometric FeTe compound indicate the presence of frustrated AFM ground states. There are very close energies and magnetic moments for the double stripe configurations, with the AFM axes oriented either on the basal plane or along the [0 0 1] direction. Presumably, both these configurations can be realized in Fe1+yTe single crystals, depending on the variations of the excess iron. This can provide different signs of magnetic anisotropy in the AFM phase, presently observed in the Fe1+yTe samples. For these types of AFM configuration, the calculations for the FeTe values of Δχ are consistent with our experimental data.
BibTeX:
@article{grechnev2014iii,
  author = {Grechnev, G. E. and Panfilov, A. S. and Fedorchenko, A. V. and Lyogenkaya, A. A. and Zhuravleva, I. P. and Chareev, D. A. and Nekrasov, A. N. and Mitrofanova, E. S. and Volkova, O. S. and Vasiliev, A. N. and Eriksson, O.},
  title = {Anisotropy of magnetic properties of Fe1+yTe},
  journal = {Journal of Physics: Condensed Matter},
  year = {2014},
  volume = {26},
  number = {43},
  pages = {436003},
  doi = {http://dx.doi.org/10.1088/0953-8984/26/43/436003}
}
Panfilov A.S., Pashchenko V.A., Grechnev G.E., Desnenko V.A., Fedorchenko A.V., Bludov A.N., Gnatchenko S.L., Chareev D.A., Mitrofanova E.S., Vasiliev A.N. Interrelation of superconductivity and magnetism in FeSe1-xTex compounds. Pressure effects 2014 Low Temperature Physics
Vol. 40(7), pp. 615-620 
DOI   PDF  
Abstract: The effect of isotropic pressures P up to 5 kbar on the superconducting transition temperature Tc of the FeSe1-xTex system (x=0, 0.85, 0.88, 0.90) is studied. For the first time, a change in the sign of the effect of pressure on Tc on going from FeSe to the tellurium-rich alloys is observed. This makes it possible to specify more precisely the form of the dependence of the pressure derivative dTc/dP on composition in this system. This dependence is compared with first principles calculations of the electron structure and magnetism of FeSe, FeTe, and FeSe0.5Te0.5 as functions of pressure, as well as with our earlier experimental data on the effect of pressure on the magnetic susceptibility of the normal state in FeSe and FeTe. This comparison is indicative of a competitive interrelationship between superconductivity and magnetism in tellurium rich FeSe1-xTex compounds.
BibTeX:
@article{panfilov2014,
  author = {Panfilov, A. S. and Pashchenko, V. A. and Grechnev, G. E. and Desnenko, V. A. and Fedorchenko, A. V. and Bludov, A. N. and Gnatchenko, S. L. and Chareev, D. A. and Mitrofanova, E. S. and Vasiliev, A. N.},
  title = {Interrelation of superconductivity and magnetism in FeSe1-xTex compounds. Pressure effects},
  journal = {Low Temperature Physics},
  year = {2014},
  volume = {40},
  number = {7},
  pages = {615-620},
  doi = {http://dx.doi.org/10.1063/1.4890990}
}
Grechnev G.E., Lyogenkaya A.A., Pluzhnikov V.B., Svechkarev I.V., Fedorchenko A.V., Perz J.M. De Haas-van Alphen effect in the band antiferromagnet FeGe2: Development of spin splitting 2014 Low Temperature Physics
Vol. 40(4), pp. 384-387 
DOI   PDF  
Abstract: The de Haas-van Alphen (dHvA) effect in the antiferromagnetic compound FeGe2 is studied experimentally. A sharp suppression of the amplitude of the first harmonic of the dHvA oscillations is observed for a number of orbits on the Fermi surface of FeGe2. The change in the conditions for suppression of the amplitude ("spin zeroes") when FeGe2 is doped with cobalt is determined. A method for analyzing the experimental data is proposed in which the g-factors of the conduction electrons are computed on the basis of calculations of the spin-polarized electron structure of the band antiferromagnet taking spin-orbital interactions into account. The exchange enhancement factor for spin paramagnetism in FeGe2 is also calculated.
BibTeX:
@article{grechnev2014ii,
  author = {Grechnev, G. E. and Lyogenkaya, A. A. and Pluzhnikov, V. B. and Svechkarev, I. V. and Fedorchenko, A. V. and Perz, J. M.},
  title = {De Haas-van Alphen effect in the band antiferromagnet FeGe2: Development of spin splitting},
  journal = {Low Temperature Physics},
  year = {2014},
  volume = {40},
  number = {4},
  pages = {384-387},
  doi = {http://dx.doi.org/10.1063/1.4871750}
}
Grechnev G.E., Logosha A.V., Lyogenkaya A.A., Grechnev A.G., Fedorchenko A.V. Electronic structure and properties of novel layered superconductors 2014 Ukrainian Journal of Physics
Vol. 59(3), pp. 284-291 
DOI   PDF  
Abstract: The electronic energy structures and magnetic properties of layered superconductors RNi2B2C, RFe4Al8, and FeSe are systematically studied, by using the density functional theory (DFT). The calculations allowed us to reveal a number of features of the electronic structure, which can cause the manifestation of peculiar structural, magnetic and superconducting properties of these systems. It is demonstrated that the Fermi energy EF is located close to the pronounced peaks of the electronic density of states (DOS). The main contribution to DOS at the Fermi level arises from 3d-electrons. The calculations of the pressure-dependent electronic structure and the magnetic susceptibility in the normal state indicate that the novel superconductors are very close to a magnetic instability with dominating spin paramagnetism. It is shown that experimental data on the pressure dependence of the superconducting transition temperature in FeSe correlate qualitatively with the calculated behavior of DOS at EF as a function of the pressure.
BibTeX:
@article{grechnev2014,
  author = {Grechnev, G. E. and Logosha, A. V. and Lyogenkaya, A. A. and Grechnev, A. G. and Fedorchenko, A. V.},
  title = {Electronic structure and properties of novel layered superconductors},
  journal = {Ukrainian Journal of Physics},
  year = {2014},
  volume = {59},
  number = {3},
  pages = {284-291},
  doi = {http://dx.doi.org/10.15407/ujpe59.03.0284}
}
Grechnev G.E., Desnenko V.A., Fedorchenko A.V., Panfilov A.S., Kolesnichenko Y.A., Khrapatiy S.V., Prylutskyy Y.I., Matzui L.Y., Ritter U., Scharff P. Magnetic properties of N-doped multi-walled carbon nanotubes 2013 Materialwissenschaft und Werkstofftechnik
Vol. 44(2-3), pp. 136-138 
DOI   PDF  
Abstract: The magnetic properties of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) were studied in the temperature and magnetic field range of (4.2-290) K and (0.05-30) kOe, respectively. Also magnetic properties of the reference MWCNTs without nitrogen doping were investigated on the same footing for comparison. The presence of iron-based particles inside N-MWCNTs was detected. The low temperature SQUID (Superconducting Quantum Interference Device) magnetization measurements were supplemented with thermogravimetric analysis. The magnetic characterization provided the saturation magnetic moment MS and residual magnetization MR of N-MWCNTs to be, respectively, 4.5 emu/g and 0.9 emu/g, whereas for the reference MWCNTs the corresponding parameters are found to be about twice higher. The coercive field value amounts to 800 Oe for both systems at low temperatures, then decreasing to about 450 Oe at 200 K.
BibTeX:
@article{grechnev2013ii,
  author = {Grechnev, G. E. and Desnenko, V. A. and Fedorchenko, A. V. and Panfilov, A. S. and Kolesnichenko, Y. A. and Khrapatiy, S. V. and Prylutskyy, Y. I. and Matzui, L. Y. and Ritter, U. and Scharff, P.},
  title = {Magnetic properties of N-doped multi-walled carbon nanotubes},
  journal = {Materialwissenschaft und Werkstofftechnik},
  year = {2013},
  volume = {44},
  number = {2-3},
  pages = {136-138},
  doi = {http://dx.doi.org/10.1002/mawe.201300083}
}
Grechnev G.E., Panfilov A.S., Desnenko V.A., Fedorchenko A.V., Gnatchenko S.L., Chareev D.A., Volkova O.S., Vasiliev A.N. Magnetic properties of superconducting FeSe in the normal state 2013 Journal of Physics: Condensed Matter
Vol. 25(4), pp. 046004 
DOI   PDF  
Abstract: A detailed magnetization study for the novel FeSe superconductor is carried out to investigate the behavior of the intrinsic magnetic susceptibility χ in the normal state with temperature and under hydrostatic pressure. The temperature dependences of χ and its anisotropy Δχ = χp-χo are measured for FeSe single crystals in the temperature range 4.2-300 K, and a substantial growth of susceptibility with temperature is revealed. The observed anisotropy Δχ is very large and comparable to the averaged susceptibility at low temperatures. For a polycrystalline sample of FeSe, the significant pressure effect on χ is determined to be essentially dependent on temperature. Ab initio calculations of the pressure-dependent electronic structure and magnetic susceptibility indicate that FeSe is close to magnetic instability, with dominating enhanced spin paramagnetism. The calculated paramagnetic susceptibility exhibits a strong dependence on the unit cell volume and especially on the height Z of chalcogen species from the Fe plane. The change of Z under pressure determines a large positive pressure effect on χ, which is observed at low temperatures. It is shown that the literature experimental data on the strong and nonmonotonic pressure dependence of the superconducting transition temperature in FeSe correlate qualitatively with the calculated behavior of the density of electronic states at the Fermi level.
BibTeX:
@article{grechnev2013,
  author = {Grechnev, G. E. and Panfilov, A. S. and Desnenko, V. A. and Fedorchenko, A. V. and Gnatchenko, S. L. and Chareev, D. A. and Volkova, O. S. and Vasiliev, A. N.},
  title = {Magnetic properties of superconducting FeSe in the normal state},
  journal = {Journal of Physics: Condensed Matter},
  year = {2013},
  volume = {25},
  number = {4},
  pages = {046004},
  doi = {http://dx.doi.org/10.1088/0953-8984/25/4/046004}
}
Grechnev G.E., Panfilov A.S., Desnenko V.A., Fedorchenko A.V., Zhuravleva I.P., Gnatchenko S.L., Tsurkan V., Chareev D.A., Kozlyakova E.S., Volkova O.S., Vasiliev A.N. Pressure effects on electronic structure and magnetic properties of the FeSe(Te) superconductors 2012 High Pressure Physics and Technics
Vol. 22(4), pp. 28-38 
URL  PDF  
Abstract: The magnetic susceptibility χ of the FeSe and FeTe compounds, which form the simplest FeSe(Te) system of the novel iron-based superconductors, is studied in the normal state under hydrostatic pressure. A substantial positive pressure effect on χ is detected at low temperatures for both compounds. At room temperature, this effect is found to be also strong, but it is negative for FeSe and positive for FeTe. Ab initio calculations of the pressure dependent electronic structure and magnetic susceptibility indicate that FeSe and FeTe are close to magnetic instability with dominating enhanced spin paramagnetism. The calculated paramagnetic susceptibility exhibits a strong dependence on the unit cell volume and the height Z of chalcogen species from the Fe plane. The observed large positive pressure effects on χ in FeTe and FeSe at low temperatures are related to considerable sensitivity of the paramagnetism to the internal parameter Z. It is shown that available experimental data on the strong and nonmonotonic pressure dependence of the superconducting transition temperature in FeSe correlate qualitatively with the calculated behavior of the density of electronic states at the Fermi level.
BibTeX:
@article{grechnev2012iii,
  author = {Grechnev, G. E. and Panfilov, A. S. and Desnenko, V. A. and Fedorchenko, A. V. and Zhuravleva, I. P. and Gnatchenko, S. L. and Tsurkan, V. and Chareev, D. A. and Kozlyakova, E. S. and Volkova, O. S. and Vasiliev, A. N.},
  title = {Pressure effects on electronic structure and magnetic properties of the FeSe(Te) superconductors},
  journal = {High Pressure Physics and Technics},
  year = {2012},
  volume = {22},
  number = {4},
  pages = {28-38},
  url = {http://www.fti.dn.ua/site/wp-content/uploads/2014/02/2012_4_3.pdf}
}
Lukienko I.N., Kharchenko N.F., Khrustalev V.M., Savytskiy V.N., Fedorchenko A.V., Desnenko V.A., Stetsenko A.N., Zorchenko V.V. Reduction of superparamagnetic clusters in the [Co/Cu(111)]n nanofilms, induced by the quantum size effect 2012 Low Temperature Physics
Vol. 38(9), pp. 848-853 
DOI   PDF  
Abstract: It is known that the quantum size effects are important for the formation of morphological properties of metal films. The regularities in the behavior of the superparamagnetic magnetoresistive effect in multilayer nanofilms Co/Cu(111) in a magnetic field, found in the work, indicate the influence of the electron size effect on the formation of clusters in these films. The results of measurements of the high-field magnetoresistive effect are reported for multilayer films [Co/Cu(111)]20 with a constant thickness of cobalt layers and the thickness of copper layer varying from film to film. It is found that an effective size of superparamagnetic formations is reduced in the films with thickness of the copper layers corresponding to the maxima of the antiferromagnetic exchange coupling between cobalt layers. It is suggested that the observed "grinding" of superparamagnetic particles is caused by oscillating changes in the electron density in the interface layer Co/Cu, induced by electron quantum size effect in the copper layers.
BibTeX:
@article{lukienko2012,
  author = {Lukienko, I. N. and Kharchenko, N. F. and Khrustalev, V. M. and Savytskiy, V. N. and Fedorchenko, A. V. and Desnenko, V. A. and Stetsenko, A. N. and Zorchenko, V. V.},
  title = {Reduction of superparamagnetic clusters in the [Co/Cu(111)]n nanofilms, induced by the quantum size effect},
  journal = {Low Temperature Physics},
  year = {2012},
  volume = {38},
  number = {9},
  pages = {848-853},
  doi = {http://dx.doi.org/10.1063/1.4752100}
}
Desnenko V.A., Rykova A.I., Sirenko V.A., Fedorchenko A.V., Cherny A.S., Khatsko E.N., Eremenko A.V. Magnetic phase segregation and glass nature of Pr0.4Bi0.3Ca0.3MnO3 manganite 2012 Low Temperature Physics
Vol. 38(3), pp. 206-209 
DOI   PDF  
Abstract: The results of detailed investigations of magnetic properties of Pr0.4Bi0.3Ca0.3MnO3 manganites at low temperatures are presented. The performed investigations of temperature, field and frequency dependences of magnetization and susceptibility as well as the magnetization relaxation processes indicate that below TC = 44 K the manganite Pr0.4Bi0.3Ca0.3MnO3 is in the magnetic phase-segregated state with ferromagnetic inclusions forming a cluster glass.
BibTeX:
@article{desnenko2012,
  author = {Desnenko, V. A. and Rykova, A. I. and Sirenko, V. A. and Fedorchenko, A. V. and Cherny, A. S. and Khatsko, E. N. and Eremenko, A. V.},
  title = {Magnetic phase segregation and glass nature of Pr0.4Bi0.3Ca0.3MnO3 manganite},
  journal = {Low Temperature Physics},
  year = {2012},
  volume = {38},
  number = {3},
  pages = {206-209},
  doi = {http://dx.doi.org/10.1063/1.3693578}
}
Grechnev G.E., Panfilov A.S., Fedorchenko A.V., Desnenko V.A., Gnatchenko S.L., Tsurkan V., Deisenhofer J., Loidl A., Chareev D.A., Volkova O.S., Vasiliev A.N. Magnetic properties of novel FeSe(Te) superconductors 2012 Journal of Magnetism and Magnetic Materials
Vol. 324(21), pp. 3460-3463 
DOI   PDF  
Abstract: Magnetization studies were carried out for the novel FeSe1-xTex superconductors (0≤x≤1) to investigate a behavior of the intrinsic magnetic susceptibility χ in the normal state. The magnetic susceptibility was found to increase gradually with Te content. The temperature dependencies of the magnetic susceptibility χ and its anisotropy Δχ= χ∥- χ⊥ were measured for FeSe in the temperature range 4.2-300 K, and a growth of susceptibility with temperature was revealed. For FeTe a substantial increase of χ under pressure was found. Ab initio calculations of the band structure and magnetic susceptibility have shown, that FeSe1-xTex systems are close to magnetic instability with dominating enhanced spin paramagnetism. The calculated paramagnetic susceptibility exhibits a strong dependence on the unit cell volume V and especially the height of chalcogen species from the Fe plane. With appropriate values of these parameters the calculations have reproduced the experimental data on χ(T) and χ(P) for FeSe and FeTe, respectively.
BibTeX:
@article{grechnev2012,
  author = {Grechnev, G. E. and Panfilov, A. S. and Fedorchenko, A. V. and Desnenko, V. A. and Gnatchenko, S. L. and Tsurkan, V. and Deisenhofer, J. and Loidl, A. and Chareev, D. A. and Volkova, O. S. and Vasiliev, A. N.},
  title = {Magnetic properties of novel FeSe(Te) superconductors},
  journal = {Journal of Magnetism and Magnetic Materials},
  year = {2012},
  volume = {324},
  number = {21},
  pages = {3460-3463},
  doi = {http://dx.doi.org/10.1016/j.jmmm.2012.02.065}
}
Grechnev G.E., Panfilov A.S., Fedorchenko A.V., Desnenko V.A., Zhuravleva I.P., Gnatchenko S.L., Chareev D.A., Volkova O.S., Vasiliev A.N. Electronic structure and magnetism of Fe-based superconductors 2012 Ukrainian Journal of Physics
Vol. 57(2), pp. 171-176 
URL  PDF  
Abstract: Ab initio calculations of the electronic structures are carried out for the novel FeSe1-xTex superconductors to explain the experimentally found anomalous magnetic properties in the normal state. The calculations have shown that FeSe1-xTex systems are close to a magnetic instability with dominating enhanced spin paramagnetism. The magnetic susceptibility is found to increase gradually with the Te content. The temperature dependences of the magnetic susceptibility χ and its anisotropy Δχ = χII - χ⊥ are investigated for FeSe, and a growth of the susceptibility with the temperature is revealed in the temperature range 4.2-300 K. For FeTe, a substantial increase of χ under pressure is found. The calculated paramagnetic susceptibility exhibits a strong dependence on the unit cell volume V and especially the height of chalcogen species from the Fe plane. The calculations have explained the experimental data on χ(T) and χ(P) for FeSe and FeTe, respectively.
BibTeX:
@article{grechnev2012ii,
  author = {Grechnev, G. E. and Panfilov, A. S. and Fedorchenko, A. V. and Desnenko, V. A. and Zhuravleva, I. P. and Gnatchenko, S. L. and Chareev, D. A. and Volkova, O. S. and Vasiliev, A. N.},
  title = {Electronic structure and magnetism of Fe-based superconductors},
  journal = {Ukrainian Journal of Physics},
  year = {2012},
  volume = {57},
  number = {2},
  pages = {171-176},
  url = {http://ujp.bitp.kiev.ua/files/journals/57/2/570212p.pdf}
}
Fedorchenko A.V., Grechnev G.E., Desnenko V.A., Panfilov A.S., Gnatchenko S.L., Tsurkan V., Deisenhofer J., Loidl A., Volkova O.S., Vasiliev A.N. Pressure effects on the magnetic susceptibility of FeTex (x ≃ 1.0) 2011 Journal of Physics: Condensed Matter
Vol. 23(32), pp. 325701 
DOI   PDF  
Abstract: The magnetic susceptibility χ of FeTex compounds (x ≃ 1.0) was studied under hydrostatic pressure up to 2 kbar at fixed temperatures of 55, 78 and 300K. Measurements were taken both for polycrystalline and single crystalline samples. At ambient pressure, with decreasing temperature a drastic drop in χ(T) was confirmed at T ≃ 70 K, which appears to be closely related to antiferromagnetic ordering. The obtained results have revealed a puzzling growth of susceptibility under pressure, and this effect is enhanced by lowering the temperature. To shed light on the pressure effects in the magnetic properties of FeTe, abinitio calculations of its volume dependent band structure and the exchange enhanced paramagnetic susceptibility were performed within the local spin density approximation.
BibTeX:
@article{fedorchenko2011ii,
  author = {Fedorchenko, A. V. and Grechnev, G. E. and Desnenko, V. A. and Panfilov, A. S. and Gnatchenko, S. L. and Tsurkan, V. and Deisenhofer, J. and Loidl, A. and Volkova, O. S. and Vasiliev, A. N.},
  title = {Pressure effects on the magnetic susceptibility of FeTex (x ≃ 1.0)},
  journal = {Journal of Physics: Condensed Matter},
  year = {2011},
  volume = {23},
  number = {32},
  pages = {325701},
  doi = {http://dx.doi.org/10.1088/0953-8984/23/32/325701}
}
Ritter U., Scharff P., Grechnev G.E., Desnenko V.A., Fedorchenko A.V., Panfilov A.S., Prylutskyy Y.I., Kolesnichenko Y.A. Structure and magnetic properties of multi-walled carbon nanotubes modified with cobalt 2011 Carbon
Vol. 49(13), pp. 4443-4448 
DOI   PDF  
Abstract: The magnetic properties of multi-walled carbon nanotubes (MWCNTs) modified with cobalt nanoparticles were studied in the temperatures and magnetic field range of (4.2-290) K and (0.03-5) T, respectively. Nanoparticles of cobalt encapsulated inside MWCNTs were obtained by using the chemical vapor deposition technique. The low temperature SQUID magnetization measurements were supplemented with structural investigations by means of high-resolution transmission electron microscopy, scanning electron microscopy as well as thermogravimetric and X-ray diffraction analysis. X-ray diffraction revealed the presence of MWCNTs, f.c.c. Co and h.c.p. Co phases. The magnetic characterization provided the remanent magnetization value (MR) of about 0.07 emu/g (∼40% of the saturation moment), while the coercive field (HC) value amounts to 600 Oe. Both parameters MR and HC slightly decrease with the rise of temperature. The substantial magnetization increase observed at low temperatures suggests the existence of nano Co clusters (in the atomic scale size).
BibTeX:
@article{ritter2011,
  author = {Ritter, U. and Scharff, P. and Grechnev, G. E. and Desnenko, V. A. and Fedorchenko, A. V. and Panfilov, A. S. and Prylutskyy, Yu. I. and Kolesnichenko, Yu. A.},
  title = {Structure and magnetic properties of multi-walled carbon nanotubes modified with cobalt},
  journal = {Carbon},
  year = {2011},
  volume = {49},
  number = {13},
  pages = {4443-4448},
  doi = {http://dx.doi.org/10.1016/j.carbon.2011.06.039}
}
Fedorchenko A.V., Grechnev G.E., Desnenko V.A., Panfilov A.S., Gnatchenko S.L., Tsurkan V.V., Deisenhofer J., Krug von Nidda H.-A., Loidl A., Chareev D.A., Volkova O.S., Vasiliev A.N. Magnetic and superconducting properties of FeSe1-xTex (x∼0, 0.5, and 1.0) 2011 Low Temperature Physics
Vol. 37(1), pp. 83-89 
DOI   PDF  
Abstract: The magnetization of FeSe1-xTex (x∼0, 0.5, and 1.0) compounds has been studied in magnetic fields up to 50 kOe and at temperatures of 2-300 K. The superconducting transition was observed at Tc∼8 K and 13.6-14.2 K in FeSe0.963 and FeSe0.5Te0.5, respectively. For most of the samples, nonlinearity of the magnetization curves in the normal state gives evidence of a common, substantial presence of ferromagnetic impurities in these compounds. By taking these impurity effects into account, the intrinsic magnetic susceptibility χ of FeSe0.963, FeSe0.5Te0.5, and FeTe was estimated to increase gradually with Te content. For FeTe a drastic drop in χ(T) with decreasing temperature was found at TN∼70 K, which is presumably related to antiferromagnetic ordering. To shed light on the observed magnetic properties, ab initio calculations of the exchange enhanced magnetic susceptibility are performed for FeSe and FeTe in the local spin density approximation.
BibTeX:
@article{fedorchenko2011,
  author = {Fedorchenko, A. V. and Grechnev, G. E. and Desnenko, V. A. and Panfilov, A. S. and Gnatchenko, S. L. and Tsurkan, V. V. and Deisenhofer, J. and Krug von Nidda, H.-A. and Loidl, A. and Chareev, D. A. and Volkova, O. S. and Vasiliev, A. N.},
  title = {Magnetic and superconducting properties of FeSe1-xTex (x∼0, 0.5, and 1.0)},
  journal = {Low Temperature Physics},
  year = {2011},
  volume = {37},
  number = {1},
  pages = {83-89},
  doi = {http://dx.doi.org/10.1063/1.3552132}
}
Grechnev G.E., Desnenko V.A., Fedorchenko A.V., Panfilov A.S., Prylutskyy Y.I., Grybova M.I., Matzui L.Y., Ritter U., Scharff P., Kolesnichenko Y.A. Magnetic properties of multi-walled carbon nanotubes modified with cobalt 2011 Materialwissenschaft und Werkstofftechnik
Vol. 42(1), pp. 29-32 
DOI   PDF  
Abstract: Magnetic properties of multi-walled carbon nanotubes (MWCNT) modified with cobalt were studied in detail in the temperature range (4.2-290) K. MWCNT which encapsulate Co nanoparticles were obtained using CVD methods. The low temperature SQUID magnetization measurements were supplemented by structural investigations with thermogravimetric analysis, HRTEM and SEM.
BibTeX:
@article{grechnev2011,
  author = {Grechnev, G. E. and Desnenko, V. A. and Fedorchenko, A. V. and Panfilov, A. S. and Prylutskyy, Y. I. and Grybova, M. I. and Matzui, L. Y. and Ritter, U. and Scharff, P. and Kolesnichenko, Y. A.},
  title = {Magnetic properties of multi-walled carbon nanotubes modified with cobalt},
  journal = {Materialwissenschaft und Werkstofftechnik},
  year = {2011},
  volume = {42},
  number = {1},
  pages = {29-32},
  doi = {http://dx.doi.org/10.1002/mawe.201100725}
}
Grechnev G.E., Desnenko V.A., Fedorchenko A.V., Panfilov A.S., Gnatchenko S.L., Zhuravleva I.P., Volkova O.S., Vasiliev A.N., Tsurkan V.V. Pressure effect on electronic structure and magnetic properties of iron-based high Tc superconductors 2010 High Pressure Physics and Technics
Vol. 20(4), pp. 60-69 
URL  PDF  
Abstract: Pressure effects on electronic structure and magnetic properties of iron-based superconductors FeSe1-xTex (x ~ 0, 0.5 and 1.0) and LaFeAsO are investigated. The superconducting transition was observed at TC ~ 8, 13.6-14.2, and 26 K in FeSe0.963, FeSe0.5Te0.5, and LaFeAsO0.85F0.1, respectively. The intrinsic magnetic susceptibility χ in the series of FeSe0.963, FeSe0.5Te0.5 and FeTe is found to increase gradually approximately 10 times as much with Te content. A kink in the low-field dependence of χ(T) was detected at TM ~ 135 K for LaFeAsO0.85F0.1. The electronic structures and paramagnetic susceptibilities of the studied compounds are calculated ab initio in external magnetic field as a function of atomic volume and structural parameter Z, which specifies the relative height of chalcogen atoms above iron plane. The calculated field-induced magnetic moments and their volume derivatives indicate that these systems are in a close proximity to a quantum critical point. For FeSe and FeTe the calculated paramagnetic susceptibilities reveal a large magnetovolume effect and a drastic sensitivity to parameter Z.
BibTeX:
@article{grechnev2010ii,
  author = {Grechnev, G. E. and Desnenko, V. A. and Fedorchenko, A. V. and Panfilov, A. S. and Gnatchenko, S. L. and Zhuravleva, I. P. and Volkova, O. S. and Vasiliev, A. N. and Tsurkan, V. V.},
  title = {Pressure effect on electronic structure and magnetic properties of iron-based high Tc superconductors},
  journal = {High Pressure Physics and Technics},
  year = {2010},
  volume = {20},
  number = {4},
  pages = {60-69},
  url = {http://www.fti.dn.ua/site/wp-content/uploads/2014/02/2010_4_6.pdf}
}
Grechnev G.E., Desnenko V.A., Fedorchenko A.V., Panfilov A.S., Kolesnichenko Y.A., Matzui L.Y., Grybova M.I., Prylutskyy Y.I., Ritter U., Scharff P. Structure and magnetic properties of multi-walled carbon nanotubes modified with iron 2010 Low Temperature Physics
Vol. 36(12), pp. 1086-1090 
DOI   PDF  
Abstract: Magnetic properties of multi-walled carbon nanotubes modified with iron (MWCNT+Fe) are studied in detail in the temperature range 4.2-300K. Carbon encapsulated Fe nanoparticles were produced by chemical vapor deposition. Low-temperature SQUID magnetization measurements are supplemented by structural studies employing thermogravimetric (TG) analysis, transmission electron microscopy (TEM), x-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM). The magnetic susceptibility of MWCNT+Fe was also studied above room temperature to provide a complete picture of its magnetic phase transitions.
BibTeX:
@article{grechnev2010,
  author = {Grechnev, G. E. and Desnenko, V. A. and Fedorchenko, A. V. and Panfilov, A. S. and Kolesnichenko, Y. A. and Matzui, L. Y. and Grybova, M. I. and Prylutskyy, Y. I. and Ritter, U. and Scharff, P.},
  title = {Structure and magnetic properties of multi-walled carbon nanotubes modified with iron},
  journal = {Low Temperature Physics},
  year = {2010},
  volume = {36},
  number = {12},
  pages = {1086-1090},
  doi = {http://dx.doi.org/10.1063/1.3530422}
}
Fedorchenko A.V., Grechnev G.E., Desnenko V.A., Panfilov A.S., Volkova O.S., Vasiliev A.N. Magnetic properties and electronic structure of LaFeAsO0.85F0.1 2010 Low Temperature Physics
Vol. 36(3), pp. 230-235 
DOI   PDF  
Abstract: The magnetic properties of the compound LaFeAsO0.85F0.1 were investigated by measurements of the dc magnetization for different values of the magnetic field H=0.02, 1.0 and 2.0T in the temperature range 4.2-300K. Superconducting behavior was found below 26K, whereas a distinct peculiarity in the low-field dependence of the magnetic susceptibility χ(T) was clearly observed at TM≃135K, which resembles a weak ferromagnetic (FM) response with saturation magnetic moment of about 10-4μB per formula unit at 50K. The transition at TM is presumably not governed by magnetic impurities but rather correlated with the antiferromagnetic (AFM) transition in undoped LaFeAsO at about the same temperature. We suggest that the observed magnetic properties of the LaFeAsO0.85F0.1 sample are due to an interplay of FM and AFM transitions, and are presumably related with an intrinsic feature of a small portion of the undoped LaFeAsO phase inherent in our sample. In order to shed light on the problem of magnetic instability of the LaFeAsO, ab initio DFT calculations of the electronic structure and paramagnetic susceptibility were performed within the local spin density approximation. It is shown that a V-shaped peculiarity in the density of electronic states close to the Fermi level can govern magnetic properties of LaFeAsO with fluorine doping and/or oxygen deficiency.
BibTeX:
@article{fedorchenko2010ii,
  author = {Fedorchenko, A. V. and Grechnev, G. E. and Desnenko, V. A. and Panfilov, A. S. and Volkova, O. S. and Vasiliev, A. N.},
  title = {Magnetic properties and electronic structure of LaFeAsO0.85F0.1},
  journal = {Low Temperature Physics},
  year = {2010},
  volume = {36},
  number = {3},
  pages = {230-235},
  doi = {http://dx.doi.org/10.1063/1.3331507}
}
Fedorchenko A.V., Lyakhno V.Y., Shnyrkov V.I. SQUID magnetometer for structuroscopy of structural materials 2010 Problems of Atomic Science and Technology
Vol. 65(1), pp. 150-156 
URL  PDF  
Abstract: We present a design of a magnetometer intended for early diagnostics of radiation damages in structural materials. The magnetometer is an rf SQUID material susceptometer based on a helium cryostat shield. The features and characteristics of such magnetometers are analyzed, the upper limit parameters achievable in the used schemes are estimated. The design of main parts, the key parameters optimization methods, the operation and calibration algorithms are described. The interference sources while measuring magnetic properties of the materials in fields B=3...4 T are revealed. The techniques to suppress external electromagnetic noises due to special design of the cryostat shield are offered. Some examples of the meter output signals and the best values of the sensitivity to sample magnetic moment variations, of the sample temperature stability, and of the liquid helium evaporation rate are given.
BibTeX:
@article{fedorchenko2010,
  author = {Fedorchenko, A. V. and Lyakhno, V. Y. and Shnyrkov, V. I.},
  title = {SQUID magnetometer for structuroscopy of structural materials},
  journal = {Problems of Atomic Science and Technology},
  year = {2010},
  volume = {65},
  number = {1},
  pages = {150-156},
  url = {http://vant.kipt.kharkov.ua/ARTICLE/VANT_2010_1/article_2010_1_150.pdf}
}
Fedorchenko A.V., Grechnev G.E., Panfilov A.S., Logosha A.V., Svechkarev I.V., Filippov V.B., Lyashchenko A.B., Evdokimova A.V. Anisotropy of the magnetic properties and the electronic structure of transition-metal diborides 2009 Low Temperature Physics
Vol. 35(11), pp. 862-868 
DOI   PDF  
Abstract: The temperature dependences of the magnetic susceptibility and its anisotropy Δχ=χ∥-χ⊥ have been measured for hexagonal single crystals of transition-metal diborides MB2 (M=Sc,Ti,V,Zr,Hf) in the temperature interval 4.2-300 K. It is found that the anisotropy ΔX is weakly temperature-dependent, a nonmonotonic function of the filling of the hybridized p-d conduction band, and largest for group-IV transition metals. First-principles calculations of the electronic structure of diborides and the values of the paramagnetic contributions (spin and Van Vleck) to their susceptibility show that the behavior of the magnetic anisotropy is due to the competition between Van Vleck paramagnetism and orbital diamagnetism of the conduction electrons.
BibTeX:
@article{fedorchenko2009,
  author = {Fedorchenko, A. V. and Grechnev, G. E. and Panfilov, A. S. and Logosha, A. V. and Svechkarev, I. V. and Filippov, V. B. and Lyashchenko, A. B. and Evdokimova, A. V.},
  title = {Anisotropy of the magnetic properties and the electronic structure of transition-metal diborides},
  journal = {Low Temperature Physics},
  year = {2009},
  volume = {35},
  number = {11},
  pages = {862-868},
  doi = {http://dx.doi.org/10.1063/1.3266916}
}
Grechnev G.E., Panfilov A.S., Fedorchenko A.V., Filippov V.B., Lyashchenko A.B., Vasiliev A.N. Effect of pressure on the magnetic properties of CrB2 2009 Low Temperature Physics
Vol. 35(7), pp. 531-535 
DOI   PDF  
Abstract: The magnetic susceptibility χ of the itinerant antiferromagnet CrB2 with TN≃87 K is studied as a function of the hydrostatic pressure up to 2 kbar at fixed temperatures 78 and 300 K. The pressure effect χ on is found to be negative in sign and weakly dependent on the magnetic state of the compound. In addition, the measured pressure dependence of the Néel temperature, dTN/dP=0. 1±0.1 K/kbar, is roughly two orders of magnitude smaller than the corresponding value for the pure chromium. The main contributions to χ and their volume dependence are calculated ab initio within the local spin density approximation, and they turn out to be in close agreement with the experimental data.
BibTeX:
@article{grechnev2009ii,
  author = {Grechnev, G. E. and Panfilov, A. S. and Fedorchenko, A. V. and Filippov, V. B. and Lyashchenko, A. B. and Vasiliev, A. N.},
  title = {Effect of pressure on the magnetic properties of CrB2},
  journal = {Low Temperature Physics},
  year = {2009},
  volume = {35},
  number = {7},
  pages = {531-535},
  doi = {http://dx.doi.org/10.1063/1.3168639}
}
Lyakhno V.Y., Fedorchenko A.V., Kivirenko O.B., Shnyrkov V.I. FRP Dewar for measurements in high pulsed magnetic fields 2009 Cryogenics
Vol. 49(8), pp. 425-428 
DOI   PDF  
Abstract: We describe a liquid helium glass-fibre reinforced plastic (G-FRP) Dewar which we designed, fabricated and tested for excitation spectrum measurements in high pulsed magnetic fields of up to 50 T. The sensitivity of high-resolution magnetic measurements carried out at low temperatures in such high fields is limited inevitably by magnetic and electric properties of the structural Dewar materials involved. Magnetic properties of various G-FRP Dewar-purpose materials are explored with a χ-meter furnished with a RF SQUID magnetometer. The Dewar materials and multilayer insulation effects contributing to the magnetic response signal are analyzed. It has also been discovered that field noise caused by the magnetization of the Dewar materials can be suppressed substantially by using special glass-epoxy technologies. The liquid helium evaporation rate is 3.8 l/day while the hold time is 27 h, the influencing factors are discussed.
BibTeX:
@article{lyakhno2009,
  author = {Lyakhno, V. Yu. and Fedorchenko, A. V. and Kivirenko, O. B. and Shnyrkov, V. I.},
  title = {FRP Dewar for measurements in high pulsed magnetic fields},
  journal = {Cryogenics},
  year = {2009},
  volume = {49},
  number = {8},
  pages = {425-428},
  doi = {http://dx.doi.org/10.1016/j.cryogenics.2009.06.004}
}
Azhazha V.M., Desnenko V.A., Ozhigov L.S., Azhazha Z.S., Svechkaryov I.V., Fedorchenko A.V. The use of magnetic methods for investigating the structure evolution in austenitic stainless steels after a long-term service at nuclear power plant units 2009 Problems of Atomic Science and Technology
Vol. 62(4), pp. 241-246 
URL  PDF  
Abstract: Investigation of the influence on magnetic properties of metals after lengthy operation in power generating units of NPS is carried out by SQUID magnetometer for austenitic steels. The obtained results testify to the high sensitivity of magnetic method on analysis of structure state of materials and point to the prospects of its use for diagnostics of low-magnetic steels.
BibTeX:
@article{azhazha2009,
  author = {Azhazha, V. M. and Desnenko, V. A. and Ozhigov, L. S. and Azhazha, Zh. S. and Svechkaryov, I. V. and Fedorchenko, A. V.},
  title = {The use of magnetic methods for investigating the structure evolution in austenitic stainless steels after a long-term service at nuclear power plant units},
  journal = {Problems of Atomic Science and Technology},
  year = {2009},
  volume = {62},
  number = {4},
  pages = {241-246},
  url = {http://vant.kipt.kharkov.ua/ARTICLE/VANT_2009_4/article_2009_4_241.pdf}
}
Grechnev G.E., Fedorchenko A.V., Logosha A.V., Panfilov A.S., Svechkarev I.V., Filippov V.B., Lyashchenko A.B., Evdokimova A.V. Electronic structure and magnetic properties of transition metal diborides 2009 Journal of Alloys and Compounds
Vol. 481(1-2), pp. 75-80 
DOI   PDF  
Abstract: The temperature dependencies of the magnetic susceptibility χ and its anisotropy Δχ=χ∥-χ⊥ were measured for the hexagonal single crystalline TB2 compounds (T = Sc, Ti, Zr, Hf, V and Cr) in the temperature range 4.2-300 K. It was found that Δ χ varies strongly and nonmonotonously with the filling of the hybridized d-band, being almost temperature independent and the largest for the diborides of group 4 metals. Ab initio calculations of the electronic structure and susceptibility of the diborides provide evidence that magnetic anisotropy originates from competing Van Vleck paramagnetism and the orbital diamagnetism of conduction electrons.
BibTeX:
@article{grechnev2009,
  author = {Grechnev, G. E. and Fedorchenko, A. V. and Logosha, A. V. and Panfilov, A. S. and Svechkarev, I. V. and Filippov, V. B. and Lyashchenko, A. B. and Evdokimova, A. V.},
  title = {Electronic structure and magnetic properties of transition metal diborides},
  journal = {Journal of Alloys and Compounds},
  year = {2009},
  volume = {481},
  number = {1-2},
  pages = {75-80},
  doi = {http://dx.doi.org/10.1016/j.jallcom.2009.03.123}
}
Grechnev G.E., Panfilov A.S., Fedorchenko A.V., Svechkarev I.V., Filippov V.B., Lyashchenko A.B., Vasiliev A.N. Pressure effects on electronic structure and magnetic properties of anisotropic metallic compounds 2008 High Pressure Physics and Technics
Vol. 18(4), pp. 112-118 
URL  PDF  
Abstract: Pressure effects on electronic structure and magnetic properties of anisotropic metallic materials (CrB2, FeGe2, LaFeAsO) are investigated. Magnetic susceptibilities of CrB2 and FeGe2 compounds were studied under hydrostatic pressure at fixed temperatures, 77 and 300 K. In order to analyze the experimental magnetovolume effects, the electronic structures were calculated ab initio in external magnetic field as a function of atomic volume by employing a full-potential LMTO method. The calculated field-induced magnetic moments and their volume derivatives compare favorably with the experimental pressure effects in magnetic properties of CrB2 and FeGe2. The main role of pressure in high-Tc superconductivity of LaFeAsO is found to reduce density of states at the Fermi level and to suppress ferromagnetic spin fluctuations.
BibTeX:
@article{grechnev2008,
  author = {Grechnev, G. E. and Panfilov, A. S. and Fedorchenko, A. V. and Svechkarev, I. V. and Filippov, V. B. and Lyashchenko, A. B. and Vasiliev, A. N.},
  title = {Pressure effects on electronic structure and magnetic properties of anisotropic metallic compounds},
  journal = {High Pressure Physics and Technics},
  year = {2008},
  volume = {18},
  number = {4},
  pages = {112-118},
  url = {http://www.fti.dn.ua/site/en/ftvd-journal/journal-content/ftvd-v18-4/}
}
Eremenko V., Gammel P., Remenyi G., Sirenko V., Panfilov A., Desnenko V., Ibulaev V., Fedorchenko A. Magnetostriction of charge density wave superconductor 2006 AIP Conference Proceedings
Vol. 850(1), pp. 979-980 
DOI   PDF  
Abstract: Single crystals of layered niobium diselenide (2H-NbSe2) compound with hexagonally packed layers were studied in a range of temperature 1.5-300 K by measuring magnetostricrtion and magnetization in field up to 20 T. The data are compared with magnetic susceptibility measurements. Specific features of measured temperature and field dependences were observed near CDW transition temperature (32.5 K) and superconducting transition (7.2 K), sensitive to magnetic field direction and strength.
BibTeX:
@article{eremenko2006,
  author = {Eremenko, V. and Gammel, P. and Remenyi, G. and Sirenko, V. and Panfilov, A. and Desnenko, V. and Ibulaev, V. and Fedorchenko, A.},
  title = {Magnetostriction of charge density wave superconductor},
  journal = {AIP Conference Proceedings},
  year = {2006},
  volume = {850},
  number = {1},
  pages = {979-980},
  doi = {http://dx.doi.org/10.1063/1.2355033}
}
Desnenko V.A., Dolya S.N., Isaev N.V., Svechkarev I.V., Fedorchenko A.V. Anomalous diamagnetism in aluminum-lithium alloys 2004 Low Temperature Physics
Vol. 30(5), pp. 425-427 
DOI   PDF  
Abstract: In the region of the equilibrium solid solutions of lithium in aluminum an anomalous low-temperature peak of diamagnetism is observed which is due to the presence of a boundary point on a line of band degeneracy directly below the Fermi level. The position and structure of the peak in the average valence function are analogous to those studied previously in the aging systems Al-Mg and Al-Zn under suitable heat treatment. The value of the lithium impurity scattering parameter for the electron states in the vicinity of the point of degeneracy mentioned is estimated, and the linear relation of that parameter with impurity-related electrical resistance in aluminum alloys is established.
BibTeX:
@article{desnenko2004,
  author = {Desnenko, V. A. and Dolya, S. N. and Isaev, N. V. and Svechkarev, I. V. and Fedorchenko, A. V.},
  title = {Anomalous diamagnetism in aluminum-lithium alloys},
  journal = {Low Temperature Physics},
  year = {2004},
  volume = {30},
  number = {5},
  pages = {425-427},
  doi = {http://dx.doi.org/10.1063/1.1739165}
}