Enhancement of Critical Current Density in low level Al-doped MgB2

TL;DR

This study demonstrates that low-level Al doping in MgB2 enhances critical current densities, especially at lower temperatures and fields, by increasing the upper critical field through alloying effects.

Contribution

It provides new insights into how Al doping improves MgB2's superconducting performance by increasing Hc2 and Jc without significantly affecting Tc.

Findings

Jc improved by up to 20 times at 5T for 1 at.% Al doping

Lattice parameters decrease confirming Al substitution

Hc2 increases with Al doping

Abstract

Two sets of MgB2 samples doped with up to 5 at. % of Al were prepared in different laboratories using different procedures. Decreases in the a and c lattice parameters were observed with Al doping confirming Al substitution onto the Mg site. The critical temperature (Tc) remained largely unchanged with Al doping. For 1 - 2.5 at.% doping, at 20K the in-field critical current densities (Jc's) were enhanced, particularly at lower fields. At 5K, in-field Jc was markedly improved, e.g. at 5T Jc was enhanced by a factor of 20 for a doping level of 1 at.% Al. The improved Jcs correlate with increased sample resistivity indicative of an increase in the upper critical field, Hc2, through alloying.