First-principles study of robust half-metallic ferromagnetism and electronic structure of the Heusler compounds Co_2-xCr_xMnGe

Abstract

Half-metallic ferromagnets (HMFs) are among the most promising materials in 
the field of spintronics because of their distinct band structures, which consist of two 
characteristic subbands, one with semiconductor-like behaviour and the other with metallic 
features. Using density functional theory-based calculations, we have carried out in-depth 
studies to predict the effects of Co replacement by Cr on electronic structure as well as the 
magnetic properties of Co2-xCrxMnGe with 0 ≤ x ≤ 1. The results demonstrate that the alloys 
are stable in the ferromagnetic phase with half-metallic nature. The origin of ferromagnetism 
can be explained by Ruderman-Kittel-Kasuya-Yosida (RKKY), like exchange interaction. Due 
to their high Curie temperatures, which increase linearly with the total magnetic moment, all 
alloys are suitable for applications at and above room temperature. Besides, the electronic 
properties have revealed a transition from half-metallic to semi-metallic character for higher 
doping concentration (x=0.75, x=1.0). The calculated total magnetic moments, however, 
decrease with increasing doping concentration, consistent with the Slater-Pauling rule. The 
observed high value of spin polarisation of all the studied compounds suggests their futuristic 
roadmaps for possible spintronics applications beyond room temperature.