Magnetic susceptibility of Co 4+( d5) in octahedral and tetrahedral environments

Abstract

Measurements of magnetic susceptibility on compounds containing stoichiometric Co 4+ are reported. The compound Ba 2CoO 4 has the Co 4+( d 5) ion at a tetrahedral site and displays a susceptibility of the expected magnitude for S = 5 2 . The compounds Ba 3Co 2CO 9 and BaCoO 3 have the Co 4+ at an octahedral site and show a susceptibility expected for low spin, S = 1 2 . For the low spin case significant deviations from Kotani's calculated susceptibility were observed. Improvement of the theory was made through incorporation of the effects of distortion from perfect octahedral symmetry and the inclusion of higher electronic configurations above t 5 2 in the 2 T 2 ground state. A case of low spin Ni in octahedral environment is also reported.