Calculations of the optical and EPR spectral data for Cr3+ion in Y3Ga5O12crystal from the complete diagonalisation method

The complete diagonalisation (of energy matrix) method is applied in this paper to calculate together the optical and electron paramagnetic resonance (EPR) spectral data for Cr3+ ion at the trigonal Ga3+ site of Y3Ga5O12 crystal. The method is founded on the two-spin-orbit-parameter model where in addition to the contributions from the spin-orbit parameter of central dn ion (i.e., one-spin-orbit-parameter model) in the traditional crystal field theory, those from the spin-orbit parameter of ligand ion via covalence effect is also considered. The calculated results propose that by using only four adjustable parameters, the 12 observed spectral data (nine optical band positions and three EPR parameters g//, g⊥ and D) in Y3Ga5O12: Cr3+ are reasonably explained. The impurity-induced local lattice distortion of Cr3+ in Y3Ga5O12 crystal is also estimated through the calculations. The results are discussed.