Search results

1

Negative Magnetoresistance of Layered High-t_{c} Compounds

100%

Medvedev Y., Yampolskii S., Lewandowski S.

Acta Physica Polonica A

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1999

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vol. 96

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issue 3-4

501-504

EN

Magnetoresistance of layered high-T_{c} systems with quasi-two-dimensional superconductivity in magnetic field H applied parallel to superconducting planes was investigated theoretically. In such configuration an increase in the magnetic field intensity decreases the critical temperature of superconducting regions. It causes both a suppression of the gap parameter Δ and an increase in the tunneling current between the decoupled superconducting planes and, as a consequence, leads to negative magnetoresistance. The dependence of tunneling current on H was calculated for superconducting layer thickness d_{S} smaller than the superconducting correlation length. The results can be used for analysis of current-voltage characteristics of both superconductor-insulator-superconductor and superconductor-insulator normal metal multilayered tunnel structures.

2

Fast Bolometric Response of Bulk La_{0.7}Sr_{0.3}MnO_{3} Electroceramic Structures

88%

Nikolaenko Y., Maksimov I., Medvedev Y., Ulyanov A., Grishin A.

Acta Physica Polonica A

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2000

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vol. 97

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issue 6

991-995

EN

We report on the performance of a microwave electroceramic bolometer of hybrid La_{0.7}Sr_{0.3}MnO_{3}/Al_{2}O_{3} (0.2×2×4 mm^{3}) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature. When compared with the high-T_{c} superconducting bolometers, the La_{0.7}Sr_{0.3}MnO_{3} microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T=230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.

3

Tunneling Conductivity of Manganites with Negative Magnetoresistance

76%

Medvedev Y., Tarenkov V., Svistunov V., Abaloshev A., Abalosheva I., Lewandowski S.

Acta Physica Polonica A

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2000

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vol. 97

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issue 5

827-830

EN

Tunneling investigations of ferromagnetic La_{0.6}Sr_{0.4}MnO_{3} ceramic samples showing negative magnetoresistance effect were carried out in two types of junctions: symmetric "break junctions" and asymmetric ceramics-insulator-metal junctions. The results are consistent with the presence of small ferromagnetic clusters in the insulating barriers of both types of junctions and suggest a two-phase state realized by impurity mechanism of phase separation.

4

Inelastic Relaxation of Oxygen and Low-Field Magnetoresistance in La_{0.65}Ca_{0.35}MnO_3 Films on Ferroelectric Ceramics Substrates

76%

Medvedev Y., Mezin N., Nikolaenko Y., Pigur A., Shishkova N., Ishchuk V., Chukanova I.

Acta Physica Polonica A

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2004

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vol. 106

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issue 6

853-859

EN

Galvanomagnetic properties of polycrystalline La_{0.65}Ca_{0.35}MnO_3 films with a thickness of 0.2~μm deposited onto Pb_{2.9}Ba_{0.05}Sr_{0.05}(Zr_{0.4}Ti_{0.6})O_3 ferroelectric ceramics substrates were investigated. We discovered an irreversible increase in film resistance after numerous inversions of substrate polarization. This phenomenon was investigated several times for three film structures. The typical duration of the process of a monotonic 3-5 times increase in film resistance was 3-6 hours. The long-time relaxation of macroscopic film resistance is explained by dielectrization of film intercrystallite boundaries. The typical size of crystallites of both the film and the substrate is 3-10μm. Such small size explains the fact of macroscopic homogeneity of film conductivity, when the specific resistance increases from 1.8×10^{-2} to 1.8Ω cm. A growth in resistance of narrow (10 nm) regions of film is explained by the redistribution of oxygen anions under the action of inhomogeneous mechanical stress. The stress between crystallites appears due to inverse piezoelectric effect of ferroelectric substrate. The magnitude of diffusion coefficient of oxygen is estimated to be D≥10^{-20} m^2 s^{-1}.

5

Electrical Transport and Magnetic Properties of La_{2/3}Pb_{1/3}MnO_3 Thin Films

64%

Baran M., Berkowski M., Fink-Finowicki J., Lewandowski S., Szymczak H., Szymczak R., Khartchev S., Medvedev Y.

Acta Physica Polonica A

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2004

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vol. 105

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issue 1-2

115-120

EN

The magnetic and transport properties of epitaxial La_{2/3}Pb_{1/3}CuO_3 thin films deposited on SrLaGaO_4 substrate using dc magnetron sputtering technique are reported. The giant magnetoresistance effect (of about 50% at magnetic field of 1 T) was observed near the Curie temperature. Several mechanisms responsible for temperature dependence of resistivity are discussed. The effect of annealing was studied. It shifted the Curie temperature to the lower value, probably, because of the loss of oxygen.

6

Magnetic and Ferroelectric Ordering in the TbMnO_3 Film

64%

Sazanovich A., Nikolaenko Y., Paszkowicz W., Mikhaylov V., Dyakonov K., Medvedev Y., Nizhankovskii V., Dyakonov V., Szymczak H.

Acta Physica Polonica A

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2014

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vol. 125

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issue 1

128-130

EN

Measurements of magnetization and electric polarization performed for the TbMnO_3 film grown onto the single crystal [100] SrTiO_3 substrate using magnetron sputtering technique exhibit series of anomalies related to the magnetic and electric ordering of the Tb^{3+} and Mn^{3+} sublattices. The detailed temperature dependences of the electric polarization and dielectric constant of the TbMnO_3 film have shown that the ferroelectric phase appears below 30 K in magnetic field H > 1 T applied in-plane and out-of-plane of the film.

Refine search results

Negative Magnetoresistance of Layered High-t_{c} Compounds

Fast Bolometric Response of Bulk La_{0.7}Sr_{0.3}MnO_{3} Electroceramic Structures

Tunneling Conductivity of Manganites with Negative Magnetoresistance

Inelastic Relaxation of Oxygen and Low-Field Magnetoresistance in La_{0.65}Ca_{0.35}MnO_3 Films on Ferroelectric Ceramics Substrates

Electrical Transport and Magnetic Properties of La_{2/3}Pb_{1/3}MnO_3 Thin Films

Magnetic and Ferroelectric Ordering in the TbMnO_3 Film