First-principles Investigation On Magnetic Half-metallic Mateirals

Recently, as the rapid development of modern technology and dramaticallyadvancement of research methods, the exploration of new functional materialswhich have rich physical properties and applications gradually deepened. Becauseof its high Curie temperature and100%spin polarization, the half-metal materialswith magnetism which belong to Heusler alloy have attracted much attention inthe field of spintronics. While dilute magnetic semiconductor (DMS) is the key torealize the semiconductor spintronic devices. In this paper, starting from the first-principles calculations, and using the generalized gradient approximation (GGA)of the density functional theory (DFT) system, we have investigated a series ofdoping alloy material theoretically. This has provided a theoretical basis for laterlooking for new function materials.The main research work and results outlined below：1、The electronic structure and magnetic properties of L21-Mn2CoAl Heusleralloy doped with Cr atom have been investigated using first-principlescalculations. The conclusions show that, Mn2CoAl with Hg2CuTi structure is aspin-gapless semiconductor, Mn2CrAl is a magnetic half-metal. When Cr doping amount is less, the spin polarization of Mn2Co1-xCrxAl decreases with the increaseof the Cr content. While Cr content is18.75%(x=0.75), the spin polarization ofthe compound can achieve99.91%, show nearly half-metallic properties.2、The electronic structure and magnetic properties of Mn2TiGa Heusleralloy doped with transition metal (Ti, V, Cr, Mn, Fe, Co, Ni and Cu) atoms havebeen investigated using first-principles calculations. The conclusions show that,after a small amount of doping in magnetic metal Mn2TiGa, the spin polarizationof Mn2Ti0.75Ni0.25Ga and Mn2Ti0.75Cu0.25Ga is still small, while the spinpolarization of Mn2Ti0.75M0.25Ga (M=Ti, V, Cr, Mn, Fe, Co) is up more than70%,and the spin polarization of the Mn2Ti0.75Fe0.25Ga and Mn2Ti0.75Co0.25Ga can reachup to85%.3、The structural stability, electronic structure and magnetic properties ofzinc-blende BeTe semiconductors doped with transition metal (Cr, Mn, Fe, Coand Ni) atoms have been investigated using first-principles calculations. The BeTebulk materials doped with Cr and Fe are determined to be half-metallic, and thosedoped with Mn and Co are found to be semiconducting, while those doped withNi is confirmed to be metallic. These results suggest a possibility that BeTe-baseddiluted magnetic semiconductors (DMS) can be good candidates for the spintronicapplications.This paper mainly involves the theory calculation, the calculation method inthis paper are in good agreement with those used by other researchers. So thecalculation method adopted in this paper is reasonable and reliable. And it also has a certain reference value on the further experimental study.