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 Co 2-x Cr x MnGe 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.