Realization of spin gapless semiconductors: the Heusler compound Mn2CoAl

TL;DR

This paper explores the properties of the spin gapless Heusler compound Mn2CoAl, revealing its unique magnetic, electronic, and transport behaviors, and demonstrating its potential as a tunable spintronic material.

Contribution

It provides a combined theoretical and experimental analysis of Mn2CoAl, establishing it as a novel spin gapless semiconductor with distinctive magnetic and transport properties.

Findings

Mn2CoAl is a ferrimagnetic semiconductor with 2 μB magnetic moment.

The compound exhibits temperature-independent conductivity below 300 K.

Magnetoresistance sign changes with temperature and field strength.

Abstract

Recent studies have reported an interesting class of semiconductor materials that bridge the gap between semiconductors and halfmetallic ferromagnets. These materials, called spin gapless semiconductors, exhibit a bandgap in one of the spin channels and a zero bandgap in the other and thus allow for tunable spin transport. Here, a theoretical and experimental study of the spin gapless Heusler compound Mn2CoAl is presented. It turns out that Mn2CoAl is a very peculiar ferrimagnetic semiconductor with a magnetic moment of 2 {\mu}B and a high Curie temperature of 720 K. Below 300 K, the compound exhibits nearly temperature-independent conductivity, very low, temperature-independent carrier concentration, and a vanishing Seebeck coefficient. The magnetoresistance changes sign with temperature. In high fields, it is positive and non-saturating at low temperatures, but negative and saturating at high temperatures. The anomalous Hall effect is comparatively low, which is explained by the close antisymmetry of the Berry curvature for kz of opposite sign.