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1
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One-Dimensional Falicov-Kimball Model in the Strong Coupling Limit

100%
Farkašovský P., Bat'ko I.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
307-310
EN
We studied the ground state properties of the one-dimensional Falicov-Kimball model in the strong coupling limit for special periodic and aperiodic configurations of ions. The ground state phase diagrams of the model for nearest neighbor and next nearest neighbor hopping are discussed.
2
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Electrical Resistivity of CrN Thin Films

81%
Batko I., Batkova M., Lofaj F.
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vol. 126
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issue 1
415-416
EN
The work is focused on the measurements of electrical resistivity of CrN thin films deposited on glass substrates by DC-magnetron sputtering in Ar+N_{2} atmosphere. The studied samples reveal semiconducting behaviour of electrical resistivity in the whole range of tested preparation parameters (such as pressure and composition of Ar-N_{2} mixture), whereas the electrical transport regime is strongly influenced by parameters of preparation. Numerical analysis of the experimental data showed that electrical transport can be adequately described in terms of variable-range hopping conduction in selected temperature intervals. Moreover, S-shaped anomaly in ρ(T) dependence, being expected to be a consequence of phase transition to a low-temperature antiferromagnetic orthorhombic phase, has been observed for sample with the highest concentration of N_{2} in the temperature interval of 220-250 K. The obtained results indicate that technology processes typically used for preparation of CrN coatings represent a promising potential to develop also high sensitivity cryogenic sensors for high magnetic fields applications.
3
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Anomalous Transport Properties of Carbon-Doped EuB_6

52%
Batkova M., Batko I., Filipov V., Flachbart K., Sechovský V., Shitsevalova N., Šantavá E., Šebek J.
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issue 5
893-894
EN
In the presented work we report electrical, magnetic and thermal properties of EuB_{6-x}C_{x} single crystals with an estimated value of x ≈ 0.07. Our studies reveal an antiferromagnetic phase transition at T_{N} ≈ 6.7 K. Electrical resistivity at zero magnetic field shows a pronounced resistivity maximum at T_{M} ≈ 7 K, just above the antiferromagnetic phase transition temperature. With increasing applied magnetic field the maximum moves to lower temperature and becomes totally suppressed at the field of 9 T. Observed magnetoresistance is negative in the whole studied temperature range 2-20 K, yielding a ratio of ρ(0 T, 7 K)/ρ(9 T, 7 K) ≈ 2.5. The origin of such magnetoresistance is associated with formation of mixed magnetic structure in the system due to fluctuation of carbon concentration.
4
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Imaging of Magnetic Domain Structure in FeSi/Mn_{0.8}Zn_{0.2}Fe₂O₄ Composite using Magnetic Force Microscopy

52%
Streckova M., Batko I., Batkova M., Bures R., Faberova M., Dzunda R., Hadraba H., Kubena I.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
714-716
EN
Soft magnetic composite was prepared by coating the commercial FeSi powder by Mn_{0.8}Zn_{0.2}Fe₂O₄ (MnZn) ferrite, which serves as a potential dielectric phase. MnZn ferrite was prepared by the sol-gel method followed by the auto-self combustion process. The spinel structure of MnZn ferrite was analyzed by X-ray diffraction technique. The composite material was prepared by uniaxial compaction technique and sintered either by conventional or unconventional microwave method. The microwave sintering was applied in order to reduce a grain growth and decrease the overall sintering time. The microstructure of FeSi powder is formed by grains of different diameter. Magnetic force microscopy and scanning electron microscopy were used for an investigation of the correlation between the grain size, grain boundaries and magnetic domains. Magnetic force microscopy visualization of magnetic domains in the prepared soft magnetic composite brings insight into how the magnetically active coating (MnZn ferrite) influences the soft magnetic (FeSi) powder under the influence of the external magnetic field.
5
Content available remote

Charge Transport and Magnetism in Eu_{1-x}Ca_{x}B_6

42%
Glushkov V., Anisimov M., Batko I., Batkova M., Bogach A., Demishev S., Filipov V., Flachbart K., Kuznetsov A., Sannikov I., Shitsevalova N., Sluchanko N.
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issue 5
891-892
EN
Transport, magnetic and thermal properties of substitutional solid solution Eu_{1 - x}Ca_{x}B_6 single crystals (0 ≤ x ≤ 0.244) have been studied at 1.8 ≤ T ≤ 300 K and in magnetic fields up to 8 T. Calcium doping is shown to result in a metal-insulator transition, which occurs at x_{MIT} ≈ 0.2. In vicinity of metal-insulator transition the effect of colossal magnetoresistance is found to be very sensitive to Ca content, the amplitude varying from Δ = [ ρ (0)- ρ (8T)]/ρ(8T) ≈1.4×10^2 to Δ ≈ 7.5 × 10^3 for 0.14 ≤ x ≤ 0.16. The analysis of magnetic contribution to heat capacity shows that a large amount of magnetic entropy ( ≈ 30%) releases in Eu_{0.845}Ca_{0.155}B_6 when moving from the Curie temperature T_{C} ≈ 5.5 K to the characteristic one T* ≈ 30 K. This observation as well as the large amplitude of low field colossal magnetoresistance effect and the deviation of magnetic susceptibility from the Curie-Weiss law detected for x = 0.155 compound in the interval T_{C} ≤ T ≤ T* seem to be associated with magnetic phase separation induced by Ca doping.
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