Coexistence of Co3+ and Co2+ in ceramic Co3TeO6; XANES, Magnetization and first principle study

Evidence of coexistence of Co3+ with Co2+ in ceramic Co3TeO6 through XANES, DC magnetization and first principal studies is provided. XANES along with linear combination fit provide relative concentrations of Co2+ and Co3+.Temperature dependent DC magnetization exhibits the same antiferromagnetic behavior as observed in single crystal. The presence of both Co2+ and Co3+ suggests that if the later is in high spin state, the effective magnetic moment is similar to that observed in single crystal studies. In contrast, if Co3+ is in low spin state effective magnetic moment is similar to that observed in Co3O4. It is further shown that both Co2+ and Co3+ in high spin states constitute a favorable ground state through first principle calculations where Rietveld refined Synchrotron X-ray diffraction data are inputs.