Spin State Behavior in Some Cobaltites (III) and (IV) with Perovskite or Related Structure

摘要: Abstract The peculiar behaviors of trivalent (3d6) and tetravalent (3d5) cobalt ions coordinated to six oxygen atoms forming a regular or distorted octahedral site are emphasized. Low spin (LS), intermediate (IS), high (HS) electronic configurations can be considered for Co3+ (S=0, S=1, S=2) Co4+ (S=1/2, S=3/2, S=5/2) depending on the relative magnitude correlations crystal field parameters. A simple model including these effects accounts crossover has led derivation phase diagrams showing respective stability range LS, IS, HS states. Extended Huckel tight-binding density functional theory–full-potential linearized augmented plane wave calculations were carried out TlSr2CoO5 SrCoO3. Results from both techniques compared used interpret specific properties oxides, which attributed character (III) (IV). Unlike in molecular compounds where only magnetic optical modified, transitions (intraatomic electron transfer) strongly coupled with metal–insulator ionocovalent oxides. Spin equilibrium lead partly occupied energy bands as nonintegral oxidation state does mixed valence and, furthermore, ordering occur upon cooling way similar charge ordering.