中文摘要：

运用群论和分子轨道理论的方法,系统地研究了非掺杂磁性半导体中阳离子空位产生磁矩的原因,并用海森堡模型阐明了磁矩之间的交换耦合机理.研究发现：阳离子空位磁矩的大小与占据缺陷能级轨道的未配对电子数有关,而缺陷能级的分布与空位的晶场对称性密切相关;通过体系的反铁磁状态和铁磁状态下的能量差估算交换耦合系数J_0,交换耦合系数J_0的正负可以用来预测磁矩之间的耦合是否为铁磁耦合：J_0〉0,则表明磁矩之间的耦合为铁磁耦合,反之为反铁磁耦合.最后指出空位的几何构型发生畸变（John-Teller效应）的原因：缺陷能级轨道简并度的降低与占据缺陷能级轨道的电子的数目有直接的关系.

英文摘要：

We use the group theory and molecular orbital theory to systematically study the origin of magnetic moment of cation-vacancy in un-doped magnetic semiconductors, and illustrate the mechanism of exchange-coupling between magnetic moments by Heisenberg model. It is found that the magnetic moment is related to the number of unpaired electrons, and the distribution of defects energy level is correlated closely with the symmetry of vacancy crystal field. The exchange-coupling coefficients J0 is estimated by the energy difference between antiferromagnetic and ferromagnetic states. And J0 can be used to predict the magnetic coupling. Positive J0 means the ferromagnetic coupling between magnetic moments, otherwise the coupling is antiferromagnetic. Moreover, we indicate that reduction of degeneracy of defect energy-level bears a direct relationship to the electron number occupied in the defect energy-level orbital, and therefore results in the structure distortion （John-Teller effect） of a cation-vacancy.