Spin Hamiltonian and structural disorder analysis for two high temperature Cr³⁺ defect centers in α-LiIO₃ crystals: Low symmetry effects

Complete diagonalization method (CDM) is developed for 3d³ ions in the trigonal type I crystal-fields (CFs). The CDM enables microscopic spin-Hamiltonian (MSH) calculations of the zero-field splitting (ZFS) parameter D and the Zeeman g-factors: g∥and g⟂. CDM/MSH program is used for CF and MSH calculations for the high temperature (HT) Cr³⁺ defect centers (A) and (B) in α-LiIO₃. The contributions to the SH parameters from the single Li⁺ vacancy and the lattice distortions are considered. The calculated SH parameters of the two HT Cr³⁺ centers agree well with the experimental ones. Structural distortions are theoretically predicted with the bond angles α and β for the Cr–O₆ complex in Cr³⁺:α-LiIO₃ greater than those in the host crystal. By incorporating the MSH approach, the comprehensive CF analysis (CFA) package for 3dN ions at arbitrary symmetry sites is at present extended as a CFA/MSH package to study SH parameters for 3d³ ions at trigonal type I CFs as well as the additional contributions to D, g∥, and g⟂ arising from the non-zero distortion angle ϕ at trigonal type II (e.g. C₃) CFs. The new finding for Cr³⁺:α-LiIO₃ is that g⟂ depends strongly on ϕ, whereas g∥and D are rather insensitive to ϕ. Copyright © 2003 Elsevier Science Ltd. All rights reserved.