The magnetic behaviour of cubic field 5T2g terms in lower symmetry

Abstract

The behaviour of the magnetic properties for the ⁵T_2g term under simultaneous perturbation by spin–orbit coupling and an asymmetric (trigonal or tetragonal) ligand field is presented. The theory is applied to the variation of the magnetic properties of nine Fe(II) octahedral complexes over the temperature range 80–300°K. The absolute magnitudes of the magnetic moments of the complexes appear to be mainly related to the t_2g electron delocalisation parameter, k. The variation with temperature depends upon the low symmetry ligand-field component and spin–orbit coupling. The magnitude and sign of the low symmetry ligand-field parameter, Δ, cannot always be unambiguously determined from the present results, although it seems unlikely to exceed ±400 cm.^–1 in nearly all the cases studied. No correlation between Δ and the nature or position of the ligand atoms is obvious.