Effect of Coherence Length in the C-Axis on Irreversibility Properties in Anisotropic High Temperature Superconductors

Abstract

Effect of coherence length on the irreversibility line is discussed based on the collective flux creep theory for anisotropic high temperature superconductors. The case of flux pinning by isotropic nonsuperconducting particles is treated. It is shown that the flux bundle size is smaller resulting in the poorer irreversibility properties for superconductors with the shorter coherence length in the c-axis for the field normal to the c-axis. When the field is applied along the c-axis, it is expected that the flux bundle size is limited to become large probably due to defects in the fluxoid lattice. This effect and the small upper critical field limit the irreversibility line. It is concluded that quasitwo-dimensional superconductors are inferior to three-dimensional ones with respect to the irreversibility properties.