Doping and disorder in the Co$_2$MnAl and Co$_2$MnGa half-metallic Heusler alloys

TL;DR

This study investigates how doping and disorder affect the electronic and magnetic properties of Co$_2$MnAl and Co$_2$MnGa half-metallic Heusler alloys, revealing that doping can preserve half-metallicity in some cases, but disorder generally destroys it.

Contribution

It provides new insights into the effects of doping and disorder on the half-metallicity of Co$_2$MnAl and Co$_2$MnGa alloys, extending previous studies to these specific compounds.

Findings

Doping with Fe and Cr can retain half-metallicity in Co$_2$MnAl.

Cr impurities show a linear increase in spin moment with concentration.

Disorder destroys half-metallicity in both alloys when excess Mn or sp atoms are present.

Abstract

We expand our study on the full-Heusler compounds [I. Galanakis \textit{et al.}, Appl. Phys. Lett. \textbf{89}, 042502 (2006)] to cover also the case of doping and disorder in the case of Co$_2$MnAl and Co$_2$MnGa half-metallic Heusler alloys. These alloys present a region of very small minority density of states instead of a real gap. Electronic structure calculations reveal that doping with Fe and Cr in the case of Co$_2$MnAl retains the half-metallicity contrary to the Co$_2$MnGa compound. Cr impurities present an unusual behavior and the spin moment of the Cr impurity scales almost linearly with the concentration of Cr atoms contrary to the Co$_2$MnZ (Z= Si, Ge, Sn) where it was almost constant. Half-metallicity is no more preserved for both Co$_2$MnAl and Co$_2$MnGa alloys when disorder occurs and there is either excess of Mn or $sp$ atoms.