中文摘要：

本文使用基于密度泛函理论的第一性原理方法研究了Co掺杂TiO_2稀磁半导体中氧空位对体系能量和磁性的影响.通过对总能量的计算发现当引入氧空位后近邻杂质体系能量高于均匀掺杂体系,同时氧空位易在Co近邻位置富集.进而发现氧空位的存在及其占位可以影响Co离子间的磁交换,近邻Co离子体系下氧空位的引入使Co离子间的铁磁耦合减弱;非近邻Co离子体系下,底面氧空位使Co离子间呈反铁磁耦合而顶点氧空位使Co离子间呈铁磁耦合.总之,氧空位的存在对Co掺杂TiO_2材料的能量及磁性都有较大影响.

英文摘要：

Dilute magnetic semiconductors have auracted much attention because of their potential applications in spintronics.In this paper, the effects of oxygen vacancy on total energy and magnetism in Co-doped T1O_2 are investigated using the density functional theory. The energy of the system with a shorter Co-Co distance is higher than that with larger Co-Co distance after introducing oxygen vacancy. Oxygen vacancy trends to congregate around the Co cations.Moreover,the strength of exchange couple reduces in the system with a shorter Co-Co distance after introducing oxygen vacancy.For the system with a larger Co-Co distance,the exchange couple between two Co impurities is anti-ferromagnetic if oxygen vacancy is located at the basal site of octahedron containing Co,and ferromagnetic if oxygen vacancy is located at the apical site of octahedron containing Co.