Electronic structure and magnetic properties of Fe₂YSi (Y = Cr, Mn, Fe, Co, Ni) Heusler alloys: A theoretical and experimental study

A series of Fe₂YSi (Y = Cr, Mn, Fe, Co, Ni) alloys were synthesized and their electronic and magnetic properties were studied both theoretically and experimentally. In particular, a novel Heusler alloy Fe ₂CrSi single phase was synthesized by means of the melt-spinning method. First principles FLAPW calculations were performed on Fe₂YSi alloys. Based on the results, Fe₂CrSi is predicted to be a half-metallic ferromagnet with a spin moment of 2μ_B/f.u. and a gap of 0.42 eV. Fe₂MnSi is also half-metallic in the ferromagnetic state. The saturation magnetic moments at 5 K for this series of alloys fit the theoretical calculations well. Specifically, the saturation magnetic moment of Fe₂CrSi is 2.05μ_B/cell, which agrees with the ideal value of 2μ_B derived from the Slater-Pauling rule. The Curie temperatures of Fe₂YSi alloys are all higher than 500 K except for Fe₂MnSi, which has a T_C below room temperature. Finally, the effect of lattice distortion on the electronic and magnetic properties of Fe₂CrSi and Fe₂CoSi was studied. It is found that Fe ₂CrSi is half-metallic from -3% to +1% uniform lattice distortion, and this character is preferred in systems containing large strain, such as melt-spun ribbons or thin films.