Investigations of electron-paramagnetic-resonance parameters of trigonal (CrO 4) 4−, (MnO 4) 3− and (FeO 4) 2− clusters in Y 2SiO 4:Cr 4+, Ba 3(VO 4) 2:Mn 5+ and K 2CrO 4:Fe 6+ crystals

Abstract

The complete high-order perturbation formulas of EPR parameters ( g-shifts Δ g ∥,Δ g ⊥ and zero-field splitting D), including not only the crystal-field (CF) mechanism, but also the charge-transfer (CT) mechanism (which is neglected in crystal-field theory), are established by a cluster approach for 3d 2 ions in trigonal symmetry. From these formulas, the EPR parameters of Y 2SiO 4:Cr 4+, Ba 3(VO 4) 2:Mn 5+ and K 2CrO 4:Fe 6+ are calculated. The results are in reasonable agreement with the observed values. It is found that the relative importance of CT mechanism increases with increasing atomic number of 3d 2 ion and so in the studies of EPR parameters for high valence state 3d n ions in crystals, both CF and CT mechanisms should be taken in account.