Increase of YBa2Cu3O7 critical currents by Mo substitution and high pressure oxygen annealing

TL;DR

This study demonstrates that Mo substitution and high-pressure oxygen annealing enhance the pinning centers in YBa2Cu3O7, significantly increasing its critical current density, especially under high magnetic fields and low temperatures.

Contribution

It provides new insights into how Mo substitution and oxygen annealing improve flux pinning and critical currents in YBa2Cu3O7 superconductors.

Findings

Mo substitution creates effective pinning centers.

High-pressure oxygen annealing further enhances pinning.

Critical current density increases significantly with Mo and oxygen treatment.

Abstract

We have previously shown for powders that Mo substitution into the CuO chains of YBa2Cu3O7 can create effective pinning centres which significantly increase the critical current density (j_c) in 7 T field by a factor of 4 and 10 at 50 and 60 K, respectively. The present work reports on the influence of the Mo substitution and high-pressure oxygen annealing on the pinning properties and critical currents of YBa_2Cu_{3-x}Mo_xO_{7-d} by comparing pure (x = 0, d > 0) and substituted (x = 0.03, d < 0) single crystals. Pinning properties have been investigated by measurements of magnetization loops and calculations of j_c in the ab-plane, in the temperature range from 2 to 90 K and in fields up to 14 T. Depending on the Mo substitution and the oxygen treatment, several types of pinning centres increasing j_c have been revealed and analysed in the frame of Dew-Hughes' and Kramer's models.