Theoretical investigations of Co2Mn1-xCrxSn and Co2MnSn1-ySiy pseudo-ternary alloys: First principles calculations

•The band structure calculations show that Co2MnSn1−ySiy alloys are half-metallic ferromagnets.•The effect of substituting Sn by Si is a slight change in the position of the Fermi level and an increase in the band gap.•For Co2Mn1−xCrxSn alloys, the results suggest that there is a finite density of states in the minority-spin d band of manganese.•The Co2Mn1−xCrxSn compounds cannot be classified as half-metallic ferromagnets.•The substitution of Mn with Cr decreases the magnetic moment per formula unit from 5.0 to 4.0µB.

The electronic and magnetic properties of Co2Mn1−xCrxSn and Co2MnSn1−ySiy alloys are investigated using density functional theory (DFT) within a full-potential linearized augmented-plane-wave (FP-LAPW) method. Amongst the systems under investigation, Co2MnSn1−ySiy alloys show half metallicity with 100% spin polarization at the Fermi level, however Co2Mn1−xCrxSn are found to be pseudo-half metals with few minority states at the Fermi level and high spin polarization. The substitution of Si with Sn keeps the magnetic moment constant in Co2MnSn1−ySiy alloys, whereas the substitution of Mn with Cr decreases the magnetic moment and degrade the half-metallicity in Co2Mn1−xCrxSn alloys. The Curie temperature is calculated and it is found to be about 928 K for all Co2MnSn1−ySiy alloys, whereas it decreases linearly with x for Co2Mn1−xCrxSn alloys. The lattices constants, bulk modulii, energy gaps, polarization ratio and density of states are calculated and their variation versus x or y are discussed.