ZnAl_2O_4:Cr^(3+)晶体局域结构研究

Investigations of lattice distortion for Cr^(3+) ions in ZnAl_2O_4 crystal

提出了新的掺杂离子局域结构畸变模型,称之为配体离子移动模型,建立了此模型下晶体微观结构与电子顺磁共振(EPR)参量之间的定量关系。首次在考虑SS(spin-spin)、SOO(spin-other-orbit)和OO(orbit-orbit)作用的基础上,采用全组态完全对角化方法,对ZnAl2O4∶Cr3+晶体的局域晶格畸变、EPR参量及其电子精细光谱进行了系统的研究,结果表明,Cr3+离子掺入ZnAl2O4晶体后,O2-离子在氧平面上向远离[111]轴的方向移动了(0.01777±0.00007)nm。从而成功地解释了ZnAl2O4∶Cr3+晶体的EPR参量。同时研究也表明,OO磁相互作用并不引起新的能级分裂,只使能级产生移动,能级移动达到10cm-1的量级,但对ZFS参量的贡献甚微。

A new lattice distortion model named ligand ions moving model was brought forward. Based on this model, the relationship between the crystal microscopic structure and EPR parameters is established. For the first time the spin-spin (SS), spin-other-orbit (SOO) and orbit-orbit (OO) interactions have also been included in the Hamiltonian, the lattice distortion, EPR parameters and electronic fine spectra for Cr3+ in ZnAl2O4 crystal have been studied using the complete diagonalization method (CDM). The theoretical results show that ligand O2- ion move (0.01777±0.00007) nm outward[111]-axis in oxygen plane. Accordingly, the EPR parameters in ZnAl2O4:Cr3+ crystal are explained successfully. At the same time, the investigations show that the OO interaction cannot split the electronic fine spectra, it can just make them moving, and the moving distance was about 10 cm-1, but the contributions to EPR parameters from the OO magnetic interaction are slight.