Nonmonotonic behavior of magnetoresistance, R(H) hysteresis, and low-temperature heat capacity of the BaPb0.75Bi0.25O3 superconductor in a magnetic field: Possible manifestations of phase separation |
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Authors: | D A Balaev A A Dubrovskiy S I Popkov K A Shaikhutdinov O N Mart’yanov and M I Petrov |
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Abstract: | The transport properties (R(T) and R(H) dependences at various values of the transport current in magnetic fields up to 65 kOe) and low-temperature heat capacity
in magnetic fields up to 90 kOe of the BaPb0.75Bi0.25O3 superconductor (T
C
≈ 11.3 K) are investigated with the goal of clarifying the mechanisms determining the nonmonotonic behavior and hysteresis
of its magnetoresistance R(H). The type of R(H) hysteretic dependences for BaPb0.75Bi0.25O3 is analogous to that observed in granular high-T
c
superconductors (HTSCs); however, unlike classical HTSC systems, the field width of the magnetoresistance hysteresis loop
for polycrystalline BaPb0.75Bi0.25O3 depends on the transport current. This means that although the mechanisms responsible for the magnetoresistance hysteresis
(the influence of the magnetic flux trapped in superconducting regions on the effective field in Josephson interlayers) are
identical in these objects, the transport current in BaPb0.75Bi0.25O3 may considerably affect the diamagnetic response of the superconductor. A considerable effect of transport current on the
field in which the R(H) dependences have a peak and exhibit hysterestic properties is observed. Such a behavior can be adequately interpreted using
the model of the spatially inhomogeneous superconductor-insulator state proposed by Gorbatsevich et al. JETP Lett. 52, 95 (1990)]. The nonmonotonic dependence of quantity C/T (C is the heat capacity) on the magnetic field discovered in the present study also agrees with the conclusions based on this
model. |
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Keywords: | |
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