KTaO_3:Cu^(2+)的电子顺磁共振参量与局域结构理论研究

Theoretical studies of EPR parameters and local defect structure for tetragonal copper center in KTaO_3

用基团模型的3d9离子在四角对称下的高阶微扰公式计算了KTaO3晶体中Cu2+杂质中心的g因子g//,g⊥和超精细结构常数A∥和A⊥。通过对四角Cu2+中心的EPR结果分析,发现杂质Cu2+占据了八面体Ta5+的位置,同时在C4轴上的最近邻出现氧空位(Vo)。由于该空位引起的静电排斥作用,Cu2+将沿C4轴在远Vo方向上位移一段距离ΔZ≈0.029 nm。在考虑了上述的缺陷结构后,各向异性g因子和超精细结构常数A因子理论值的理论计算值与实验值符合得比较好。

The electron paramagnetic resonance （EPR） parameters g factors g// , g1 and the hyperfine structure con stants A// and A⊥ for the tetragonal KTaO3 ：Cu^2＋ crystal are theoretically studied in this work. The impurity Cu^2＋ occupies the octahedral Ta5＋ site, which is attributed to a nearest-neighbouring oxygen vacancy V0 along the axis. Owing to the electrostatic repulsion between the V0 and Cu^2＋ , the Cu^2＋ is displaced away from the V0 by about 0. 29？ along the [100] axis. The theoretical values of the g and A factors are reasonable agreement with the experi mental findings.