ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
We have studied the structural, magnetic, and transport properties of polycrystalline (Nd1−xGdx)1.85Ce0.15CuO4−y; x=0.0, 0.05, 0.10, 0.25, and 0.50; produced under different atmospheres and cooling rates after the reduction process. From x-ray analysis the T′-structure is preserved for all samples studied. We also found that quenched samples in argon atmosphere exhibit superconductivity below ∼22 K. The temperature dependence of the electrical resistivity ρ(T) displays a striking double resistive superconducting transition with no evidence of a zero resistance state down to 1.5 K. The electrical resistivity has a (approximate)20% drop at the upper critical temperature Tci followed by a plateau down to a lower temperature Tcj. While Tci is both weakly dependent on the Gd content and external applied magnetic field, the behavior of ρ(T) at low temperatures is strongly sensitive to the Gd concentration, excitation current, and applied magnetic fields. Also, the behavior of ρ(T) below (approximate)3 K is almost field independent. The magnetic susceptibility data χ(T) reveal superconductivity below Tci and a reentrantlike behavior at low temperatures where the magnitude of χ(T) increases rapidly with decreasing temperature. These observations are similar to those observed in granular Ga films close to the nonmetallic side of the superconductor-insulator transition. We argue that these compounds can be understood within the framework of a superconducting granular model. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.365137
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