Researches of the optical band positions, spin-Hamiltonian parameters and defect structures for Cr 3+ -doped colquiriite-type fluoride crystals LiSrGaF 6 , LiSrAlF 6 and LiCaAlF 6

The optical and EPR data of Cr 3+ -doped colquiriite-type fluoride crystals LiSrGaF 6 , LiSrAlF 6 and LiCaAlF 6 are computed from the complete diagonalization of energy matrix method based on the two-spin-orbit-parameter model. This model takes account of the contributions due to both the spin-orbit parameter of central d n ion (in the traditional crystal field theory) and that of ligand ions via covalent effect. The computed results indicate that the observed five optical band positions and three spin-Hamiltonian parameters ( g factors g // , g ⊥ and zero-field splitting D ) can be explained reasonably with only four adjustable parameters. The defect structures of Cr 3+ centers in these crystals are also achieved from the calculations. It is suggested that the trigonal MF 6 octahedra in LiSrMF 6 : Cr 3+ (M = Al, Ga) crystals change from the compression (along C 3 axis) in the host crystals to the elongation in the Cr 3+ impurity centers. The results are discussed.