CaTiO_3中Co^(2+)离子各向异性g因子的理论研究

Investigations of the Anisotropic g Factors for Co^(2+) in CaTiO_3

利用基于离子簇模型的正交对称中3d7离子g因子微扰公式,计算了CaTiO3中Co2+的各向异性g因子gx、gy和gz,与此相关的晶场参量由杂质局部结构和重叠模型得到。研究发现,由于杂质Co2+与母体Ti4+存在电荷和离子半径的差异,将引起两个方向的键长发生5.6%的相对改变,从而导致明显的正交畸变。由此得到的g因子理论值与实验较为符合。

The anisotropic g factors gx, gy and gx, for Co^2＋ in CaTiO3 are theoretically investigated from the perturbation formulas of the g factors for a 3d7 ion in orthorhombically distorted octahedra based on the cluster approach. The related orthorhombic field parameters are determined from the local structure of the studied impurity center and the superposition model. Because the impurity Co^2＋differs from the host Ti^4＋ in ionic radius and charge, the Co-O band lengths along two directions may suffer a relative variation by about 5.6%, yielding significant orthorhombic distortion. The calculated g factors by using the above local structure are in reasonable agreement with the experimental findings.