Enhanced flux pinning in neutron irradiated MgB2

TL;DR

This study demonstrates that neutron irradiation enhances flux pinning and critical current density in MgB2 up to an optimal fluence, beyond which superconducting properties deteriorate due to excessive damage.

Contribution

It provides new insights into how neutron irradiation introduces effective pinning centers in MgB2, improving its superconducting performance.

Findings

Optimal neutron fluence enhances Jc and flux pinning.

Excessive irradiation suppresses critical temperature and Bc2.

Point-like pinning centers are effectively introduced at certain fluences.

Abstract

We study the effect of neutron irradiation on the critical current density Jc of isotopically pure polycrystalline Mg11B2 samples. For fluences in the range 1017-1018 cm-2, Jc is enhanced and its dependence on magnetic field is significantly improved: we demonstrate that, in this regime, point-like pinning centers are effectively introduced in the system proportionally to the neutron fluence. Instead, for larger fluences, a strong suppression of the critical temperature accompanied by a decrease of both the upper critical field Bc2 and Jc is found.