Properties of polycrystalline (Nd{ital {sub 1{minus}x}}Gd{ital {sub x}}){sub 1.85}Ce{sub 0.15}CuO{sub 4{minus}{ital y}} compounds
- Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05389-970, Sao Paulo (Brazil)
We have studied the structural, magnetic, and transport properties of polycrystalline (Nd{ital {sub 1{minus}x}}Gd{ital {sub x}}){sub 1.85}Ce{sub 0.15}CuO{ital {sub 4{minus}y}}; {ital 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 {ital T}{sup {prime}}-structure is preserved for all samples studied. We also found that quenched samples in argon atmosphere exhibit superconductivity below {approximately}22 K. The temperature dependence of the electrical resistivity {ital {rho}(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 {approx}20{percent} drop at the upper critical temperature {ital T}{sub ci} followed by a plateau down to a lower temperature {ital T}{sub cj}. While {ital T}{sub ci} is both weakly dependent on the Gd content and external applied magnetic field, the behavior of {ital {rho}(T)} at low temperatures is strongly sensitive to the Gd concentration, excitation current, and applied magnetic fields. Also, the behavior of {ital {rho}(T)} below {approx}3 K is almost field independent. The magnetic susceptibility data {ital {chi}(T)} reveal superconductivity below {ital T}{sub ci} and a reentrantlike behavior at low temperatures where the magnitude of {ital {chi}(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. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 496460
- Report Number(s):
- CONF-961141--
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 81; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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