Directional vortex pinning at microwave frequency in YBa$_{2}$Cu$_3$O$_{7-x}$ thin films with BaZrO$_3$ nanorods

TL;DR

This study examines how BaZrO$_3$ nanorods in YBa$_2$Cu$_3$O$_{7-x}$ thin films influence vortex pinning at microwave frequencies, revealing directional effects and anisotropic responses relevant for superconductor applications.

Contribution

It demonstrates the impact of BaZrO$_3$ nanorods on directional vortex pinning and anisotropic microwave response in YBa$_2$Cu$_3$O$_{7-x}$ films, highlighting the role of nanostructure orientation.

Findings

Nanorods induce directional vortex pinning along the c-axis.

Microwave response shows no angular scaling, indicating complex anisotropy.

Pinning effectiveness is significant over a wide angular range around the c-axis.

Abstract

We investigate the effect of the anisotropy and of the directional pinning in YBa$_2$Cu$_3$O$_{7-x}$ films grown by pulsed laser ablation from targets containing BaZrO$_3$ at 5% mol. BaZrO$_3$ inclusions self-assemble to give nanorods oriented along the c-axis, thus giving a preferential direction for vortex pinning. The directionality of vortex response is studied at high ac frequency with the complex microwave response at 48 GHz, as a function of the applied field and of the angle $\theta$ between the field and the c-axis. The complex microwave response does not exhibit any angular scaling, suggesting that the structural anisotropy of YBa$_2$Cu$_3$O$_{7-x}$ is supplemented by at least another preferred orientation. The pinning parameter $r$ shows evidence of directional pinning, effective in a wide range of angles around the c-axis (thus ascribed to BZO nanocolumns).