Structure of the flux lines lattice in NbSe2: Equilibrium state and influence of the magnetic history

TL;DR

This study uses small-angle neutron scattering to analyze the flux line lattice in Fe-doped NbSe2, revealing an ordered structure during peak effect and showing that magnetic history does not alter the lattice's order, suggesting the peak effect is not due to bulk disorder.

Contribution

It provides new insights into the flux line lattice structure and the origin of the peak effect in NbSe2, emphasizing the role of heterogeneous screening currents over bulk disorder.

Findings

Ordered flux line lattice observed during peak effect

Magnetic history does not affect lattice order

Peak effect not caused by bulk disorder

Abstract

We have performed small-angle neutron scattering (SANS) of the flux line lattice (FLL) in a Fe doped NbSe_2 sample which presents a large peak effect in the critical current. The scattered intensity and the width of the Bragg peaks of the equilibrium FLL indicate an ordered structure in the peak effect zone. The history dependence in the FLL structure has been studied using field cooled and zero field cooled procedures, and each state shows the same intensity of Bragg scattering and good orientational order. These results strongly suggest that the peak effect is unrelated to a bulk disordering transition, and confirm the role of a heterogeneous distribution of screening current.