Various Valence States of Square-Coordinated Mn in A-Site-Ordered Perovskites

A-site-ordered perovskites LaMn3Cr4O12 and LaMn3Ti4O12 were synthesized under high-pressure and high-temperature conditions. The charge formula of LaMn3Cr4O12 was found to be LaMn3+3Cr43+O12 with Mn3+ at the square-coordinated A site. The valence of the A-site Mn ions in LaMn3Ti4O12 appeared to be less than +2, and the charge combination in this compound seemed to be LaMn31.67+Ti44+O12. Although the square-coordinated A site in A-site-ordered perovskites has been widely known to be occupied by Jahn-Teller active Mn3+, the present results show that the valence of Mn at the A site can vary from +3 to possible +1.67.