Disorder-induced Phase Transition of Vortex Matter in MgB2

TL;DR

This study investigates a disorder-induced phase transition in vortex matter within MgB2, revealing a sharp peak in torque measurements that signifies a transition from a quasi-ordered to a disordered vortex glass phase.

Contribution

It provides experimental evidence of a disorder-driven phase transition in vortex matter in MgB2 using torque magnetometry.

Findings

Peak in irreversible torque at about 0.85 Hc2

Pronounced history effects between peak onset and maximum

Peak fields' dependence on angle and temperature tracks Hc2

Abstract

Measurements of single crystalline MgB2 with torque magnetometry in fields up to 90 kOe reveal a sharp peak in the irreversible torque at about 0.85 Hc2. In the region between peak onset and maximum, pronounced history effects occur. Angle and temperature dependence of the characteristic peak fields track those of Hc2. The features observed suggest that the peak marks a disorder-induced phase transition of vortex matter between a quasi-ordered Bragg glass and a highly-disordered glass.