Site Investigation of Ionic Substitution in Mn $_{3 - {\rm x}}$ Co $_{\rm x}$ O

We propose an energy diagram for the isolated Mn²⁺ free electron interacted with external field and crystal field in tetragonal spinel Mn_3-xCo_xO₄ films and provide a simple and effective way to analyze the distribution of cations via the measurement of electron spin resonance (ESR). Based on our ESR results, we suggest that Co ions prefer to enter the tetrahedral sites (A-sites) of spinel structure. However, when the amount of Co ions at A-site reach a critical value, the partial octahedral site (B-site) of Mn ions start to be replaced. With increasing Co content up to 1, the Co ions substitute both A- and B-sites simultaneously and the structure transforms into two phase at x=1.5.