Fe掺杂SnO_2稀磁半导体超精细场的第一性原理计算

Ab initio calculations of magnetic hyperfine field in Fe-doped SnO_2

采用基于密度泛函理论线性缀加平面波方法的WIEN2k程序,计算Fe掺杂SnO2稀磁半导体的电子结构和磁性,计算中性电荷态Fe0和电荷受主态Fe1-或Fe2-。结果表明,Fe掺杂SnO2的基态都是铁磁态,O空位更容易出现在Fe原子周围。中性电荷态Fe0磁矩较小,Fe1-或Fe2-态磁矩变大,并且计算的磁超精细场和磁矩与穆斯堡尔谱测量结果相符合。电子结构分析表明,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。不同电荷态下,能级分裂的程度不同,从而影响电子填充3d轨道的模式。3d轨道中未成对电子数增加,处于高自旋态的Fe原子是产生巨磁矩的原因。

Background： The study of the diluted ferromagnetic semiconductors with a curie temperature well above room temperature has been paid too much attention, which has potential applications in spin electronics. Purpose： For a better understanding of the origin of the ferromagnetism, especially in the presence of O vacancies, the microscopic electronic structure and hyperfine fields are required. Methods： An ab initio calculations magnetic hyperfine fields in the Fe doped SnO2 were performed by the Wien2k code embodying the full-potential linearized augmented plane-wave method for two charge states of the impurity that occupies two different cases of the neutral impurity state Fe^0 and the charged acceptor state Fe^1- or Fe^2-. The Fe doped SnO2 can provide one or two electrons via oxygen donor vacancies. Results： The present results illustrate clearly that the energy level splitting of the Fe-3d orbit with O vacancies and without O vacancies for the （SnO2）lsFeO2＋le and （SnO2）lsFeO2＋2e valences resulted in the increasing of the unpaired electrons and the leading of Fe atoms into the high spin states, producing the giant magnetic moment. Conclusion： The calculated Fe magnetic moment for the （SnO2）15FeO2＋1e is 5μB, which is consistent with the magnetic moment of 5.1μB measured by the M6ssbauer spectroscopy.