Effect of damage by 2-MeV He ions and annealing on Hc2 in MgB2 thin films

TL;DR

This study investigates how 2-MeV He ion damage and subsequent annealing affect the superconducting properties, especially Hc2, in MgB2 thin films, revealing damage-induced maxima and the effects of annealing.

Contribution

It provides new insights into how ion-induced damage and annealing alter the critical temperature and upper critical field in MgB2 films from different deposition methods.

Findings

Damage causes a linear decrease in Tc with residual resistivity.

Maxima in Hc2(0) are observed due to damage.

Annealing restores Tc but not the damage-induced Hc2(0) values.

Abstract

The effect of damage induced by 2-MeV alpha particles, followed by annealing, on the critical temperature (Tc), resistivity, and upper critical field (Hc2), of three MgB2 films made by different deposition processes has been studied. Damage creates a linear decrease in Tc with residual resistivity, and produces maxima in both Hc2(0)-perpendicular and Hc2(0)-parallel. Below Tcs of about 25 K, Hc2(0) depends roughly linearly on Tc, while the anisotropy of Hc2(0) decreases as Tc decreases. Annealing the films reproduces the Tc vs. residual resistivity dependence but not the Hc2(0) values induced by damage.