Manifestation of history dependent critical currents via dc and ac magnetisation measurements in single crystals of CeRu2 and 2H-NbSe2

TL;DR

This paper investigates how the critical current density in vortex states of CeRu2 and 2H-NbSe2 depends on their magnetic history, revealing a transition from disordered to ordered vortex structures influenced by field changes and shaking.

Contribution

It demonstrates the path dependence of critical current density in these superconductors and identifies conditions for restoring vortex order.

Findings

Critical current density depends on thermomagnetic history in a large (H,T) region.

Path dependence disappears above the peak effect region, indicating vortex disorder.

Disordered vortex states can be ordered by field changes or ac shaking.

Abstract

A study of path dependent effects in single crystals of CeRu2 and 2H-NbSe2 show that critical current density Jc of the vortex state depends on its thermomagnetic history over a very large part of (H,T) parameter space. The path dependence in Jc is absent above the peak position (i.e., H > Hp) of the peak effect region, which we believe identifies the complete loss of order in the vortex structure. The highly disordered FC state can be healed into a relatively ordered vortex lattice by subjecting it to a large enough change in dc field (few tens of Oe) or by shaking the FC state with sufficient ac field (few Oe).