Unifying analyses of the crystal field energy levels and EPR g factors for the trigonal Co2+ tetrahedral center in β˝-alumina

Abstract

The crystal field energy levels (obtained from the optical spectra) and g factors g//, g⊥ (obtained from EPR spectra) for the Co2+ ion at the trigonal Al3+ tetrahedral site in β˝-alumina crystal are unifiedly analyzed with the full diagonalization (of energy matrix) method founded on the two-spin-orbit-parameter model (which contains the contributions from both the spin-orbit parameters of central dn ion and ligand ion via covalence effect). The results display that by applying only three adjustable parameters, the observed ten spectral data (eight crystal field energy levels and two g factors) can be rationally interpreted, confirming the availability of this full diagonalization method in the united analyses of optical and EPR data. The large impurity-generated angular distortion and hence the large trigonal distortion [which correspond to the large g-factor anisotropy and large ground state splitting ΔE(4A2)] of the Co2+ tetrahedral center in β˝-alumina are also gained. The outcomes are discussed.