Flux penetration measurements and the harmonic magnetic response of hot isostatically pressed (Pb,Gd)Mo6S8

1089-7550

AIP Digital Archive

Physics

Detailed flux penetration measurements and the harmonic magnetic response have been measured from 4.2 K up to the critical temperature in dc fields up to 10 T for a hot isostatically pressed Chevrel-phase superconductor (Pb,Gd)Mo6S8. Good agreement is found between experimental results up to the tenth harmonic and calculations derived from a critical-state model which demonstrates that on the macroscopic scale the supercurrents flow throughout the bulk of the material. The field and temperature dependence of the critical current density shows a universal scaling behavior in agreement with Kramer's pinning law, which suggests that a single grain-boundary mechanism determines the critical current density. Complementary compositional microscopy, x-ray, resistivity, and susceptibility data are presented. When gadolinium is not incorporated into the crystal structure it acts primarily as an oxygen getter in the form Gd2S3, which enhances the density of paths of PbMo6S8 with low oxygen content and high superconducting critical parameters. When the divalent gadolinium replaces the trivalent lead to form (Pb1−xGdx)Mo6S8, it reduces the density of hole states at the Fermi energy which lowers the critical parameters, the critical current density, and the irreversibility field. © 1999 American Institute of Physics.

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