The effect of configuration interaction on the magnetic properties of Ru⁴⁺ in single cubic crystals

The d⁴ configuration in an octahedral ligand field is considered. The optical absorption spectrum of Ru⁴⁺ is calculated by taking into account the ligand-field, electrostatic and spin-orbit interactions and using all the strong-field states of the ground configuration t ⁴₂ as well as those arising from the first excited configuration t³₂e. The matrix elements of the magnetic moment operator (L + 2S) were calculated between the ground state A₁ and all the T₁ states belonging to the two configurations. These matrix elements and the wavefunctions of the energy levels were used to calculate the magnetic susceptibility of Ru⁴⁺ in cubic coordination. It was found that the effect of the t³₂e configuration on both the energy levels and the magnetic susceptibility is very large and, therefore, cannot be ignored. The covalency of the t₂ and e orbitals was also included in the calculations of the susceptibility. It was found that there is not much difference in the degree of covalency of these orbitals, and also the delocalization of the electrons is fairly small.