Spin Hamiltonian and structural disorder analysis for two high temperature Cr3+ defect centers in α-LiIO3 crystals—low symmetry effects Original Research Article

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.