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Negative Magnetoresistance of Layered High-t_{c} Compounds

100%

Medvedev Y., Yampolskii S., Lewandowski S.

vol. 96

issue 3-4

501-504

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.

Two-Dimensional Behavior of YBa_{2}Cu_{3}O_{x} Films on SrTiO_{3} Substrates

80%

Mikheenko P. N., Lewandowski S. J.

Acta Physica Polonica A

1997

vol. 92

issue 1

152-156

Long-term (up to 18 months) degradation of textured YBa_{2}Cu_{3}O_{x} films prepared by laser ablation and magnetron sputtering on single crystal SrΤiO_{3}, MgO and Al_{2}O_{3} substrates were investigated. All films at each stage of exposition displayed a clearly visible quasi-2D behavior. From the measurements of the Kosterlitz-Thouless temperature it could be concluded that the oxygen content and density of charge carriers remained constant. It follows that the main consequence of degradation is the omission of some planes from the transport of supercurrent and the samples could be described in the model of layered structure with variable number of conducting planes. Using this model we find that effective thickness of an isolated CuO_{2} plane in samples with greatest internal damage is ≈2Å.

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2 Acta Physica Polonica A

1 1999

1 1997

1 Lewandowski S.

1 Lewandowski S. J.

1 Medvedev Y.

1 Mikheenko P. N.

1 Yampolskii S.

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Negative Magnetoresistance of Layered High-t_{c} Compounds

Two-Dimensional Behavior of YBa_{2}Cu_{3}O_{x} Films on SrTiO_{3} Substrates