Evolution of the fishtail-effect in pure and Ag-doped MG-YBCO

TL;DR

This study investigates the evolution of the fishtail-effect in pure and silver-doped YBCO superconductors through magnetic measurements, revealing how doping influences vortex pinning and magnetic behavior.

Contribution

It provides new insights into how Ag doping alters the fishtail-effect and pinning mechanisms in YBCO superconductors across a wide temperature range.

Findings

Fishtail-effect observed in a broad temperature range for both samples.

Ag doping increases the maximum magnetic field H_{max} due to additional pinning centers.

The origin of the fishtail-effect involves competition between surface barrier and bulk pinning.

Abstract

We report on magnetic measurements carried out in a textured YBa$_2$Cu$_3$O$_{7-\delta}$ and YBa$_2$(Cu$_{1-x}$Ag$_x$)$_3$O$_{7-\delta}$ (at $x \approx$ 0.02) crystals. The so-called fishtail-effect (FE) or second magnetization peak has been observed in a wide temperature range 0.4~$<T/T_c<$~0.8 for $\textbf{H}\parallel c$. The origin of the FE arises for the competition between surface barrier and bulk pinning. This is confirmed in a non-monotonically behavior of the relaxation rate $R$. The value $H_{max}$ for Ag-doped crystals is larger than for the pure one due to the presence of additional pinning centers, above all on silver atoms.