Evolution of Fishtail-effect with aging in pure and Ag-doped MG-YBCO

TL;DR

This study investigates how the fishtail-effect in MG YBCO superconductors evolves with aging, revealing the roles of bulk pinning and surface barriers across a temperature range and the impact of silver doping on pinning strength.

Contribution

It provides new experimental insights into the aging effects on the fishtail-effect and the influence of silver doping on vortex pinning in MG YBCO superconductors.

Findings

Fishtail-effect observed in both pure and Ag-doped MG YBCO crystals.

Bulk pinning dominates at low temperatures, surface barriers at high temperatures.

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

Abstract

$M(B)$-curves were experimentally investigated. Fishtail-effect (FE) was observed in MG YBa$_2$Cu$_3$O$_{7-\delta}$ and YBa$_2$Cu$_{3-x}$Ag$_x$O$_{7-\delta}$ (at $x \approx$ 0.02) crystals in a wide temperature range 40 K $<T<$ 75 K at the orientation of magnetic field $\textbf{H}\parallel c$. It was obtained that the influence of bulk pinning on FE is more effective at low temperatures while the influence of surface barriers is more effective at high temperatures. The value $H_{max}$ for Ag-doped crystals is larger than for a pure one that due to the presence of additional pinning centers, above all on silver atoms.