Effects of Zn on the grain boundary properties of La2-xSrxCu1-yZnyO4 superconductors

TL;DR

This study investigates how zinc impurities affect the grain boundary properties and superconducting coupling in La2-xSrxCu1-yZnyO4 superconductors, revealing that Zn suppresses critical temperature and intergrain coupling depending on hole content and disorder.

Contribution

It provides a systematic analysis of zinc's impact on grain boundary coupling and critical temperature in La214 superconductors using ac susceptibility measurements.

Findings

Zn suppresses Tc and Tgcp similarly across samples.

Hole content and Zn-induced disorder significantly influence grain boundary coupling.

Zn doping affects the intergrain shielding current and superconducting transition.

Abstract

The properties of the grain boundaries (GBs) are of significant importance in high-Tc cuprates. Most large scale applications of cuprate superconductors involve usage of sintered compounds. The critical current density and the ability to trap high magnetic flux inside the sample depend largely on the quality of the GBs. Zn has the ability to pin vortices but it also degrades superconductivity. In this study we have investigated the effect of Zn impurity on the intergrain coupling properties in high-quality La2-xSrxCu1-yZnyO4 sintered samples with different hole concentrations, p (\equiv x), over a wide range of Zn contents (y) using field-dependent ac susceptibility (ACS) measurements. The ACS results enabled us to determine the superconducting transition temperature Tc, and the temperature Tgcp, at which the randomly oriented superconducting grains become coupled as a function of hole and disorder contents. We have analyzed the behavior of the GBs from the systematic evolution of the values of Tgcp(p, y), Tc(p, y), and from the contribution to the field-dependent ACS signal coming from the intergrain shielding current. Zn suppresses both Tc and Tgcp in a similar fashion. The hole content and the carrier localization due to Zn substitution seem to have significant effect on the coupling properties of the GBs. We have discussed the possible implications of these findings in detail in this article. PACS: 74.72.Dn; 74.62.Dh; 74.25.Sv Keywords: Zn doped La214; Critical current density; Grain boundary