Study On Band Structure Regulation Mn₂-based Half-metal Materials

Heusler alloy has attracted more and more people’s attention since found, physical properties and application of its rich functions, make it become the important source of the development of new functional materials, and in the aerospace, computer, medical and other fields has great use value. The article embarks from the first calculation principle, based on density functional theory, using the Generalized Gradient Approximation, the theoretical research on a series of alloy after doping, provide theoretical basis for the experiment.Main achievements summarized as follows:1.The Mn32Co16-XFeXSn16(0<X≤4) series alloy using First Principles calculation has carried on the theoretical research. When mixed Fe elements, band gap width by Fe elements added to change, the decrease of spin flip. Mn(A) and Mn(B) are arranged in parallel, is different from not doped with parallel arrangement. Due to the incorporation of the Fe alloy from to the ferromagnetic antiferromagnetic transition.2. By first principles calculation, Mn and Sn double for a doping control Mn2 CoGa alloy band structure, obtained a new kind of spin without the band gap semiconductor alloy Mn2.25 Co0.75 Ga0.5 Sn0.5. Transition group elements doping can adjust spin up and spin down band gap width, the main group elements doping can adjust the spin splitting of the material and the Fermi surface3. Summarized the Electron-counting Rules, analysis of origin, half band gap opened up to explore new means of a metal. Put forward the point of view:(1) In different semimetal Heusler compounds found in the three types of electronic counting rules: Mt = Zt- 18, Mt = Zt- 24 and Mt = Zt- 28;(2) A metal band gap may appear in spin up band;(3) Different Heusler alloy to comply with the same electronic counting rules, originated in the half metal band gap by different mechanism.