Trigonal Distortions of the Cr3+ Octahedral Centers in Cr3+-Doped ABO3 (A = Sc, In, Lu) Crystals Obtained by Analyzing EPR Data

Abstract

The spin-Hamiltonian parameters (g factors g_//, g_⊥ and zero-field splitting D) of the trigonal Cr³⁺ centers in Cr³⁺-doped ABO₃ (A = Sc, In, Lu) borate crystals are computed from both the complete diagonalization (of energy matrix) method and also the perturbation method based on the two-spin–orbit-parameter model, where the contributions to spin-Hamiltonian parameters due to both the spin–orbit parameter of central dⁿ ion and that of ligands via covalence effect are considered. The calculated results are compatible with those available in experiments. The defect structures of the trigonal (CrO₆)⁹⁻ octahedral centers are also evaluated from the calculations. It is found that the trigonal (MO₆)⁹⁻ octahedra change from the elongation in the host crystals to the compression in the impurity centers because of the large size and nature mismatch substitution in these Cr³⁺-doped ABO₃ crystals. The results are discussed.