Angular dependence of the high-frequency vortex response in YBa$_2$Cu$_3$O$_{7-x}$ thin film with self-assembled BaZrO$_3$ nanorods

TL;DR

This study investigates how the vortex response in YBCO thin films with BZO nanorods varies with angle at high frequencies, revealing effective pinning by nanorods and extending anisotropic vortex motion models.

Contribution

It provides a detailed analysis of angular dependence of vortex dynamics in BZO-doped YBCO, introducing an extended model based on intrinsic anisotropy and nanorod pinning effects.

Findings

BZO nanorods are highly effective pinning centers even in tilted magnetic fields.

The flux-flow resistivity scales with a reduced field function of angle.

Pinning mechanisms vary with angle, involving nanorods and intrinsic YBCO properties.

Abstract

We present a microwave study of the angular dependence of the flux-flow resistivity $\rho_{ff}$ and of the pinning constant $k_p$ in YBCO thin films containing BZO nanorods. We find that BZO nanorods are very efficient pinning centers, even in tilted fields. We find that $\rho_{ff}$ is a scaling function of a reduced field $H/f(\theta)$. We extend a model for the anisotropic motion of vortices in uniaxially anisotropic superconductor, able to describe the experimental $f(\theta)$ on the basis of only the intrinsic anisotropy of YBCO. The pinning constant $k_p$, by contrast, exhibits different field dependences in different angular ranges, consistent with pinning by BZO at angles as large as 60$^{\circ}$, and with pinning along the $a,b$ planes as originating from the same mechanism as in pure YBCO with the field along the c axis.