Substituting the main group element in cobalt - iron based Heusler alloys: Co$_2$FeAl$_{1-x}$Si$_x$

TL;DR

This study uses electronic structure calculations to explore how substituting Al with Si in Co$_2$FeAl$_{1-x}$Si$_x$ Heusler alloys affects their electronic and magnetic properties, revealing stable half-metallic ferromagnetism.

Contribution

It provides new insights into the impact of main group element substitution on the electronic structure and magnetic stability of Co-Fe-based Heusler alloys.

Findings

Substitution increases valence electrons, acting as electron doping.

The alloys exhibit half-metallic ferromagnetism.

Electron doping stabilizes the minority spin gap at x=0.5.

Abstract

This work reports about electronic structure calculations for the Heusler compound Co$_2$FeAl$_{1-x}$Si$_x$. Particular emphasis was put on the role of the main group element in this compound. The substitution of Al by Si leads to an increase of the number of valence electrons with increasing Si content and may be seen as electron-doping. Self-consistent electronic structure calculations were performed to investigate the consequences of the electron doping for the magnetic properties. The series Co$_2$FeAl$_{1-x}$Si$_x$ is found to exhibit half-metallic ferromagnetism and the magnetic moment follows the Slater-Pauling rule. It is shown that the electron-doping stabilises the gap in the minority states for $x=0.5$.