Electronic Structures, Magnetic Properties, And Half-metallicity Of X₂YSi（X=Cr,Mn;Y=Fe,Co,Ni）Compounds:a First-principles Study

Traditional microelectronics only using the electron’s charge, there will be some limitations to the storage density. The use of electron’s spin in spintronic devices for information processing, storage and transport, that whould greatly increase the storage density of per unit volume. The development of spintronic devices, it is needs to investigate the electronic structures, magnetism, and other properties of the materials. In the band structure of half-metallic materials, one of the spin bands shows metallic property, whereas the other spin band has semiconducting nature, thus there is100%spin polarization at the fermi level. Because of important application value in spintronics devices have been attracted widely attention of study.In many half metallic materials, heulser alloy become a research hotspot because which has high Curie temperature and with strcture similar as sphalerite structure. Based on density functional theory, we use the Full potential linearized augmented plane wave method to investigate the electronic structure, magnetic properties and half-metallic property of heusler alloy X2YSi(X=Cr, Mn; Y=Fe, Co,Ni). We considered two types of structures, i. e., Hg2CuTi and Cu3MnAl structure. Through the relationship of total energy crystal and lattice constant we obtained the optimized lattice constant in Hg2CuTi structure accordingly is5.620A (Cr2FeSi), 5.657A (Cr2CoSi),5.699A (Cr2NiSi),5.567A (Mn2FeSi),5.617A (Mn2CoSi),5.782A (Mn2NiSi). Through the relationship of total energy crystal and lattice constant we obtained the optimized lattice constant in Hg2CuTi structure accordingly is5.682A (Cr2FeSi),5.695A (Cr2CoSi),5.695A (Cr2NiSi),5.600A (Mn2FeSi),5.698A (Mn2CoSi),5.665A (Mn2NiSi). Total energy calculations show that:X2YSi (X=Cr, Mn; Y=Fe, Co, Ni) alloy with Hg2CuTi structure is more stable than that with Cu2MnAl structure. In Hg2CuTi structure, Mn2CoSi is half-metallic ferromagnet, Mn2FeSi is nearly-half-metallic ferromagnet with the total magnetic moment of3.000μB and2.014μB, which is good agreement with the Slater-Pauling rule, The width of the band gap of0.050eV (Mn2FeSi) and0.301eV (Mn2CoSi); others also ferromagnet, with total magnetic moment of-3.918μB (Mn2NiSi),-0.003μB (Cr2FeSi),1.011μB (Cr2CoSi)å'Œ1.873μB (Cr2NiSi); On the other hand, X2YSi (X=Cr, MnY=Fe, Co, Ni) alloys with the Cu2MnAl structure is conventional ferromagnetic with total magnetic moment of2.146μB (Mn2FeSi),6.296μB (Mn2CoSi),4.907μB (Mn2NiSi),0.897μB (Cr2FeSi),3.045μB (Cr2CoSi)å'Œ0.859μB (Cr2NiSi).