First-principles material design and perspective on semiconductor spintronics materials

摘要

We investigate the electronic structure and magnetic properties of III–V compound semiconductor based dilute magnetic semiconductors (DMS) from first-principles. The electronic structure of DMS is calculated by using the Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA) method in connection with the local density approximation (LDA). Describing the magnetic properties by a classical Heisenberg model, effective exchange interactions are calculated by applying magnetic force theorem for two impurities embedded in the CPA medium. With the calculated exchange interactions,T_C is estimated by using the mean field approximation, the random phase approximation and the Monte Carlo simulation. In the above compounds, the magnetic interactions are well described from double exchange picture. Due to the short-range interactions, high-T_C is difficult to achieve in the presently investigated materials. Based on the present results, two strategies towards high-T_C are proposed to realize useful DMS materials. One uses spinodal decomposition to realize high blocking temperature in super-paramagnetic blocking phenomena and the other uses co-doping method to realize high concentration doping of magnetic impurities for high-T_C.