Modification of intergrain connectivity, upper critical field anisotropy, and critical current density in ion irradiated MgB2 films

TL;DR

This study investigates how high-energy ion irradiation affects the superconducting properties of MgB2 films, revealing modifications in intergrain connectivity, critical fields, and current density depending on ion type and dose.

Contribution

It demonstrates that ion irradiation can tune the superconducting properties of MgB2 films by altering intergrain connectivity and band scattering mechanisms in a controlled manner.

Findings

Heavy ion irradiation enhances the upper critical field at low defect densities.

Light ion irradiation improves the critical current density.

Intergrain connectivity decreases with increased irradiation dose.

Abstract

We study the effect of 100 MeV Silicon and 200 MeV Gold ion irradiation on the inter and intra grain properties of superconducting thin films of Magnesium Diboride. Substantial decrease in inter-grain connectivity is observed, depending on irradiation dose and type of ions used. We establish that modification of sigma band scattering mechanism, and consequently the upper critical field and anisotropy, depends on the size and directional properties of the extrinsic defects. Post heavy ion irradiation, the upper critical field shows enhancement at a defect density that is five orders of magnitude less compared to neutron irradiation. The critical current density however is best improved through light ion irradiation.