Fe掺杂SnO2稀磁半导体超精细场计算和磁性研究

Magnetic semiconductor can simultaneously use spin and the electronic charge, which has dual characteristic of semiconductor materials and magnetic materials and merge information processing and storage into together. This material is a novel semiconductor material with very broad application prospects and is also the key material in the investigation of spintronics. The origin of magnetism in Fe doped SnO2 diluted magnetic semiconductor has much controversial in theory and experiment. This proposal will adopt the first principle code implementation of the full-potential linearized-augmented-plane-wave (FLAPW) method in the framework of density functional theory (DFT) to calculate micro-structures and the hyperfine fields including electric field gradient and magnetic hyperfine field of the Fe doped SnO2 diluted magnetic semiconductors. This proposal is expected to identify the origin of the magnetism of the Fe doped SnO2 diluted magnetic semiconductors combined calculation results with the M?ssbauer measurement and perturbed angular correlation measurement for the first time.

稀磁半导体能同时利用电子的电荷和自旋特性，具有半导体材料和磁性材料的双重特性，将信息处理与存储融合在一起，是一种非常具有广泛应用前景的新颖半导体材料，也是目前自旋电子学相关器件材料研究中的热点。具有高居里转变温度的Fe掺杂SnO2稀磁半导体研究也受到极大重视。然而理论上和实验上稀磁半导体磁性起源有很大争议。本项目采用基于密度泛函理论的线性缀加平面波的全电子方案的第一性原理程序计算不同体系的Fe掺杂SnO2 稀磁半导体的微观电子结构和超精细场（包括电场梯度和磁超精细场）。有望在国际上首次结合超精细相互作用的穆斯堡尔谱和扰动角关联测量分析确定Fe掺杂SnO2基稀磁半导体的磁性起源。

本工作采用全势全电子的WIEN2k软件包计算了Fe掺杂SnO2稀磁半导体磁超精细场，计算了无Fe掺杂的O空位和Sn空位、Fe掺杂、Fe与O空位、Fe和电子掺杂的多种体系SnO2稀磁半导体的电子结构和磁性。计算结果表明，无Fe掺杂情况下，发现本征O空位缺陷不产生磁性、Sn空位缺陷产生磁性；所有Fe掺杂SnO2体系的基态都是铁磁态；只有Fe掺杂磁矩较小，引入O空位或电子掺杂后，磁矩变大一倍以上。在O空位或电子掺杂情况下，计算的磁超精细场和磁矩与穆斯堡尔测量结果相当。掺杂一个电子的Sn15FeO32超胞的磁矩为5μB，与穆斯堡尔谱测量导出值5.1μB符合。分析表明掺杂Fe-3d轨道与氧八面体O-2p轨道相互作用，造成3d轨道能级分裂。体系不同，能级分裂程度不同，从而影响电子在3d轨道的排列。3d轨道中未成对电子数增加、Fe原子处于高自旋态是产生巨磁矩的原因。这一机制与目前提出的超交换作用和F芯交换（FCE）机制都不同。