Various Valence States of Square-Coordinated Mn inA-Site-Ordered Perovskites

摘要

A-site-ordered perovskites LaMn_3Cr_4O_12and LaMn_3Ti_12were synthesized under high-pressureand high-temperature conditions. The charge formula of LaMn_3Cr_4O_12was found to be LaMn~3+_3Cr~4O_12with Mn~3+at the square-coordinated A site. The valence of the A-site Mn ions in LaMn3Ti4O12appeared tobe less than +2, and the charge combination in this compound seemed to be LaMn~1.67+_3Ti~4+_4O_12. Althoughthe square-coordinated A site in A-site-ordered perovskites has been widely known to be occupied byJahn-Teller active Mn~3+, the present results show that valence of Mn at the A site can vary from +3to possible +1.67.