Evidence for vortex staircases in the whole angular range due to competing correlated pinning mechanisms

TL;DR

This study investigates how vortex structures in YBa2Cu3O7 crystals are influenced by various correlated pinning mechanisms, revealing vortex staircases across all angles due to competing effects.

Contribution

It demonstrates that correlated pinning mechanisms, including columnar defects and material anisotropy, induce vortex staircases throughout the entire angular range.

Findings

Sharp maximum in magnetization at high fields aligned with defect tracks

Lock-in phase with angle-independent pinning at low fields

Vortex staircases caused by interplay of defects, twins, and ab-planes

Abstract

We analyze the angular dependence of the irreversible magnetization of YBa$_2$Cu$_3$O$_7$ crystals with columnar defects inclined from the c-axis. At high fields a sharp maximum centered at the tracks' direction is observed. At low fields we identify a lock-in phase characterized by an angle-independent pinning strength and observe an angular shift of the peak towards the c-axis that originates in the material anisotropy. The interplay among columnar defects, twins and ab-planes generates a variety of staircase structures. We show that correlated pinning dominates for all field orientations.