The Role of Nonlocality in the Pinning Properties of Borocarbides Materials

TL;DR

This paper reviews how nonlocal electrodynamics influence vortex pinning in borocarbide superconductors, revealing complex anisotropic behaviors and demonstrating the impact of nonlocality on in-plane anisotropy.

Contribution

It provides the first detailed experimental analysis of nonlocal effects on vortex pinning anisotropy in borocarbides, highlighting the suppression of in-plane anisotropy by impurity levels.

Findings

Reorientation transition causes a kink in pinning force density for H || c-axis.

In-plane fourfold anisotropy is induced by nonlocal effects and can be suppressed by impurities.

Pinning force density is larger and relaxes slower when H is perpendicular to c-axis.

Abstract

An experimental review on the influence of nonlocal electrodynamics in the vortex pinning properties of non-magnetic borocarbide superconductors is presented. We show that the pinning force density Fp exhibits a rich and complex anisotropic behavior that sharply contrast with the small mass anisotropy of these compounds. For magnetic fields H applied parallel to the crystallographic c-axis, the first order reorientation transition between two rhombic lattices manifests itself as a kink in Fp(H). For H perpendicular to the c-axis, a much larger Fp(H) and a slower relaxation rate is observed. In this field configuration, nonlocality induces a fourfold periodicity in Fp when H is rotated within the square basal plane. Unlike the out-of-plane anisotropy, which persists for increasing impurity levels, the in-plane fourfold anisotropy can be strongly suppressed by reducing the electronic mean free path. This result unambiguously demonstrate that the in-plane anisotropy is a consequence of nonlocal effects.