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

摘要

A-site-ordered perovskites LaMn_3Cr_4O_(12) and LaMn_3Ti_4O_(12) were synthesized under high-pressure and high-temperature conditions. The charge formula of LaMn_3Cr_4O_(12) was found to be LaMn~(3+) _3Cr~(3+)_4O_(12) with Mn~(3+) at the square-coordinated A site. The valence of the A-site Mn ions in LaMn_3Ti_4O_(12) appeared to be less than +2, and the charge combination in this compound seemed to be LaMn~(1.67+)_3Ti~(4+)_4O_(12). Although the square-coordinated A site in A-site-ordered perovskites has been widely known to be occupied by Jahn-Teller active Mn~(3+), the present results show that the valence of Mn at the A site can vary from +3 to possible +1.67.