A new spin gapless semiconductor: quaternary Heusler CoFeCrGa alloy

TL;DR

This paper reports the discovery and experimental validation of a new spin gapless semiconductor, CoFeCrGa, with promising properties for spintronic applications, including high Curie temperature and stable electrical characteristics.

Contribution

First experimental evidence of SGS behavior in quaternary Heusler CoFeCrGa, supported by first-principles calculations and analysis of its electronic and magnetic properties.

Findings

Exhibits spin gapless semiconductor behavior with temperature-independent conductivity.

Transforms from SGS to half-metallic phase under pressure.

Has a Curie temperature exceeding 400 K, suitable for applications.

Abstract

Despite a plethora of materials suggested for spintronic applications, a new class of materials has emerged, namely spin gapless semiconductors (SGS), that offers potentially more advantageous properties than existing ones. These magnetic semiconductors exhibit a finite band gap for one spin channel and a closed gap for the other. Here, supported by the first-principles, electronic-structure calculations, we report the first experimental evidence of SGS behavior in equiatomic quaternary CoFeCrGa, having a cubic Heusler (L21) structure but exhibiting chemical disorder (DO3 structure). CoFeCrGa is found to transform from SGS to half-metallic phase under pressure, which is attributed to unique electronic-structure features. The saturation magnetization (MS) obtained at 8 K agrees with the Slater-Pauling rule and the Curie temperature (TC) is found to exceed 400 K. Carrier concentration (up to 250 K) and electrical conductivity are observed to be nearly temperature independent, prerequisites for SGS. The anomalous Hall coefficient is estimated to be 185 S/cm at 5 K. Considering the SGS properties and high TC, this material appears to be promising for spintronic applications.