Electronic structure of cation-deficient CoO from first principles

Generalized gradient approximation with correction for Hubbard energy was used to study electronic and magnetic properties of defected CoO. Vacancies were introduced into the cobalt sublattice. Calculations were performed for point defect concentrations of 3.125% and 6.25%. Trivalent cobalt ions are created in both ferromagnetic cobalt sublattices, inducing acceptor states located in the band gap of the CoO matrix. They arise from a charge transfer which converts initial divalent cobalt to trivalent state. Concentration of trivalent cobalts is twice as large as the concentration of cation vacancies. Our ab initio calculations support experimental data obtained previously by emission Mossbauer spectroscopy.