Studies of EPR g factors of the isoelectronic 3d 3 series Cr 3+, Mn 4+ and Fe 5+ in SrTiO 3 crystals

Abstract

The g-shifts Δ g(= g− g s, where g s≈2.0023 is the free-ion value) of the isoelectronic 3d 3 series Cr 3+, Mn 4+ and Fe 5+ in SrTiO 3 crystals are calculated from the high-order perturbation formula based on the cluster approach for 3d 3 ion in cubic octahedral site. The formula includes not only the contribution from the crystal-field (CF) mechanism, but also that from the charge-transfer (CT) mechanism (which is omitted in the CF theory). From the calculations, it is found that the contribution Δ g CT from the CT mechanism in sign is contrary to the corresponding Δ g CF from the CF mechanism and the relative importance of CT mechanism (characterized by |Δ g CT/Δ g CF|) increases with the increasing valence state (and hence the atomic number) of 3d 3 ion. The positive g-shift Δ g of SrTiO 3:Fe 5+ is due mainly to the contribution of CT mechanism. So, for the explanations of g factors of the high valence state 3d n ions (e.g. Mn 4+ and Fe 5+) in crystals, the contributions from both CF and CT mechanisms should be taken into account.