Anisotropic properties of MgB2 by torque magnetometry

TL;DR

This study investigates the anisotropic superconducting properties of MgB2 using torque magnetometry, revealing deviations from theoretical models near Tc and suggesting a higher anisotropy of penetration depth at low temperatures in certain magnetic fields.

Contribution

It provides experimental insights into the anisotropic behavior of MgB2, highlighting discrepancies with existing theoretical predictions and emphasizing the need for refined models.

Findings

Angular dependence of Hc2 deviates near Tc from Ginzburg-Landau theory

Anisotropy of penetration depth gamma_lambda is higher at low temperatures in fields >0.2 T

Results suggest modifications to theoretical models of MgB2's anisotropic properties

Abstract

Anisotropic properties of superconducting MgB2 obtained by torque magnetometry are compared to theoretical predictions, concentrating on two issues. Firstly, the angular dependence of Hc2 is shown to deviate close to Tc from the dependence assumed by anisotropic Ginzburg-Landau theory. Secondly, from the evaluation of torque vs angle curves it is concluded that the anisotropy of the penetration depth gamma_lambda has to be substantially higher at low temperature than theoretical estimates, at least in fields higher than 0.2 T.