The irreversibility line of overdoped Bi_{2+x}Sr_{2-(x+y)}Cu_{1+y}O_{6 +- delta} at ultra-low temperatures and high magnetic fields

TL;DR

This study measures the irreversibility line in overdoped Bi-2201 at ultra-low temperatures and high magnetic fields, finding it aligns with flux lattice melting rather than flux creep models, indicating flux melting influences magnetoresistance.

Contribution

It provides the first detailed measurement of the irreversibility line at ultra-low temperatures in Bi-2201, showing flux lattice melting as the dominant mechanism.

Findings

Irreversibility field fits flux lattice melting model

No magnetization jumps or peak effects observed

Behavior similar to resistive critical field in thin films

Abstract

The irreversible magnetization of the layered high-T_{c} superconductor Bi_{2+x}Sr_{2-(x+y)}Cu_{1+y}O_{6 +- delta} (Bi-2201) has been measured by means of a capacitive torquemeter up to B=28 T and down to T=60 mK. No magnetization jumps, peak effects or crossovers between different pinning mechanisms appear to be present. The deduced irreversibility field B_{irr} can not be described by the law B_{irr}(T)=B_{irr}(0)(1-T/T_{c})^n based on flux creep, but an excellent agreement is found with the analytical form of the melting line of the flux lattice as calculated from the Lindemann criterion. The behavior of B_{irr}(T) obtained here is very similar to the resistive critical field of a Bi-2201 thin film, suggesting that magnetoresistive experiments are likely to be strongly influenced by flux lattice melting.