Vortex dynamics and irreversibility line in optimally doped SmFeAsO$_{0.8}$F$_{0.2}$ from ac susceptibility and magnetization measurements

TL;DR

This study investigates vortex behavior and the irreversibility line in optimally doped SmFeAsO$_{0.8}$F$_{0.2}$ superconductor using ac susceptibility and magnetization measurements, revealing high critical current density and flux dynamics.

Contribution

It provides the first detailed phase diagram and flux line lattice features for this material, highlighting its potential for technological applications.

Findings

High intra-grain critical current density (~2 x 10^7 A/cm^2)

Field dependence of depinning energy follows 1/H in high fields

Phase diagram and flux lattice features characterized

Abstract

Ac susceptibility and static magnetization measurements were performed in the optimally doped SmFeAsO$_{0.8}$F$_{0.2}$ superconductor. The field - temperature phase diagram of the superconducting state was drawn and, in particular, the features of the flux line lattice derived. The dependence of the intra-grain depinning energy on the magnetic field intensity was derived in the thermally-activated flux creep framework, enlightening a typical 1/H dependence in the high-field regime. The intra-grain critical current density was extrapolated in the zero temperature and zero magnetic field limit, showing a remarkably high value $J_{c0}(0) \sim 2 \cdot 10^{7}$ A/cm$^{2}$, which demonstrates that this material is rather interesting for the potential future technological applications.