VALENCE STATE EQUILIBRIA BETWEEN COBALT AND MANGANESE IONS AND MAGNETIC-PROPERTIES OF LACO0.9MN0.1O3

According to the thermodynamic equilibria between the low spin state Co(III) (t2g6e(g)0) ion and the high spin state Co3+ (t2g4e(g)2) ion and between the cobalt and manganese ions with different valence state and spin state, an approximate semiempirical formula has been proposed to calculate the magnetic susceptibilities of La Co0.9Mn0.1O3 in a wide temperature range (100-1200 K). The results show that the calculated susceptibilities of LaCo0.9Mn0.1O3 are very close to the experimental susceptibilities, and the relative errors are smaller than 5%, except in a few cases. In LaCo0.9Mn0.1O3 there may exist the low spin state Co(III) ion, the high spin state Co3+ and Co2+ ions, and the high spin state Mn3+ and Mn4+ ions at different temperatures. The content of the low spin state Co(III) ion has been predominant in LaCo0.9Mn0.1O3 in the whole temperature range, and decreases gradually with increasing temperature. At lower temperatures, the content of the Mn4+ ion in LaCo0.9Mn0.1O3 is larger than that of the Mn3+ ion; however, at higher temperatures, the manganese ion is mainly trivalent. The calculated results are in good agreement with some experimental results; for example, the effective paramagnetic moment of the compound agrees with the paramagnetic Curie point of the compound. The temperature dependence of the electric resistivity of LaCo0.9Mn0.1O3 has also been predicted. (C) 1994 Academic Press, Inc.