Unified research on the optical and EPR spectral data for the Cr3+ion in the low-temperature trigonal phase of a LaAlO3crystal

Abstract

The crystal field energy levels (or optical band positions) and EPR parameters ( g factor g// , g ⊥ and zero-field splitting D ) for the Cr 3+ ion in the trigonal phase of a LaAlO 3 crystal are calculated together through the complete diagonalization (of energy matrix) method. The method is founded on the two-spin-orbit-parameter model in which the contributions from both the spin-orbit parameter of the central d n ion and that of the ligand ion (the latter is ignored in the conventional crystal field theory) are considered. From the calculations, the observed seven optical band positions and three EPR parameters ( g// , g ⊥, D ) for LaAlO 3 :Cr 3+ at T ≈ 4.2 K are reasonably and unifiedly explained with only four adjustable parameters, and the impurity-induced local angular distortion of the Cr 3+ center in LaAlO 3 is estimated.