Design of opto-spintronics devices and nanospin-probes

1.基于宽禁带材料GaN和ZnO的稀磁半导体（DMS）在光电子器件中的应用，已经在第一性原理计算的基础上进行了理论设计。(1)主体半导体的价带和磁性掺杂剂的3d轨道之间的相对能量位置和杂化程度对于理解DMS中的铁磁性机制是重要的。(2)通过考虑DMS中局域自旋之间的交换相互作用作为原子间距离的函数，精确地计算了DMS的居里温度。宽禁带DMS的室温铁磁性很难实现，因为交换相互作用是相当短的范围。(3)由于磁性掺杂剂之间的相互吸引作用，在DMS中预期磁性掺杂剂的不均匀分布。(4)适当的非磁性元素共掺杂可以提高DMS的居里温度。(5)在一定的铁氧体中适当掺杂非磁性元素，可以获得铁磁性.在第一性原理计算的基础上，设计了具有高自旋极化的半金属铁磁体。(1)锌掺杂的CrAs和CrSb是自旋电子器件应用的有前途的材料，因为它们与传统电子器件中使用的半导体兼容。(2)从理论上研究了半金属Heusler合金中原子无序的影响。即使在B2型无序结构中也保持高自旋极化。(3)研究了半金属铁磁体与半导体异质结的电子结构。在Heusler合金与AArnientichirtnrAAC wAlAs fnr 7inn-h17 onda或Ac/carninndiinfnr infanr之间的（110）界面上保留了高自旋极化

1. Diluted magnetic semiconductors (DMS) based on wide band-gap materials such as GaN and ZnO, which are exploited in optoelectronic device applications, have been designed theoretically on the basis of first-principles calculations. (1) The relative energy position and the degree of hybridization between the valence-band of host semiconductors and 3d orbitals of magnetic dopants are important to understand the mechanism of ferromagnetism in DMS. (2) The Curie temperature of DMS has been evaluated accurately by accounting the exchange interaction between localized spins in DMS as a function of the inter-atomic distance. Room-temperature ferromagnetism is hardly achieved for wide band-gap DMS since the exchange interaction is rather short-ranged. (3) The inhomogeneous distribution of magnetic dopants is expected in DMS due to attractive interaction between them. (4) The increase of Curie temperature is expected for DMS co-doped with non-magnetic elements appropriately. (5) The ferromagnetism could be obtained by doping non-magnetic elements appropriately into certain semiconductors.2. Half-metallic ferromagnets exhibiting high spin polarization have been designed theoretically on the basis of first-principles calculations. (1) Zinc-blende CrAs and CrSb are promising materials for spintronic device applications since they are compatible with semiconductors exploited in conventional electronic devices. (2) The influence of atomic disorder in half-metallic Heusler alloys has been examined theoretically. High spin polarization is maintained even in the B2-type disordered structure. (3) The electronic structure of hetero-junctions between half-metallic ferromagnets and semiconductors has been investigated. High spin polarization is preserved for the (110) interface between Heusler alloys And AArnientichirtnrAAC wAll As fnr 7inn-h17onda Or Ac/carninnndiinfnr inforfanne