Investigations on the EPR Parameters of KMgF₃:Cr⁺

Abstract

The electron paramagnetic resonance parameters (i.e., g factor, hyperne structure constant and superhyperne parameters) of KMgF3:Cr + are theoretically investigated from the perturbation formulae of these parameters for an octahedral 3d 5 cluster. As for the calculations of g factor and hyperne structure constant, both the contributions from the crystal-eld and charge transfer mechanisms are included based on the cluster approach. The metal to ligand charge transfer contribution to the g-shift ∆g (≈ g − 2.0023) is the same (negative) in sign and much larger in magnitude as compared to the crystal-eld one. The conventional argument that the charge transfer contributions to zero-eld splittings are negligible for 3d 5 ions in uorides is no longer suitable for ∆g analysis of KMgF3:Cr + due to the dominant second-order charge transfer perturbation term. The charge transfer contribution to hyperne structure constant exhibits the same sign and about 4% of the crystal-eld one. The unpaired spin densities of the uorine 2s, 2pσ and 2pπ orbitals are quantitatively acquired from the relationships with the relevant molecular orbital coecients using the uniform model. The present treatments are superior to the previous calculations of directly tting the experimental superhyperne parameters.