Spin Hamiltonian and structural disorder analysis for two high temperature Cr 3+ defect centers in α-LiIO 3 crystals—low symmetry effects

Abstract

Complete diagonalization method (CDM) is developed for 3d 3 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) Cr 3+ defect centers (A) and (B) in α-LiIO 3. 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 Cr 3+ centers agree well with the experimental ones. Structural distortions are theoretically predicted with the bond angles α and β for the Cr–O 6 complex in Cr 3+:α-LiIO 3 greater than those in the host crystal. By incorporating the MSH approach, the comprehensive CF analysis (CFA) package for 3d N ions at arbitrary symmetry sites is at present extended as a CFA/MSH package to study SH parameters for 3d 3 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. C 3) CFs. The new finding for Cr 3+:α-LiIO 3 is that g ⊥ depends strongly on ϕ, whereas g ∥ and D are rather insensitive to ϕ.