X-Ray emission studies of evolution of the electron and spin structures of Mn in mixed manganites [Ln.sub.1 - x][Sr.sub.x]Mn[O.sub.3]

The chemical shift [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and the exchange splitting Δ[E.sub.split] of the emission X-ray Mn [K.sub.β1] line in mixed manganites [Ln.sub.1 - x][Sr.sub.x]Mn[O.sub.3] (Ln = La, Sm, and Ce) have been systematically studied for the first time. It has been found that [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and Δ[E.sub.split] are almost the same in the range x < 0.4-0.5, as is the case in [Mn.sub.2][O.sub.3], and then they decrease relatively quickly to the values characteristic of Mn[O.sub.2]. It has been assumed that such a behavior corresponds to the model where in the region of hole doping (x < 0.5), the ground state is a mixture of configurations [Mn.sup.3+] 3[d.sup.4] and 3[d.sup.4][L.bar], so that the second configuration fraction increases with x. At high values of x, the configuration [Mn.sup.4+] 3[d.sup.3] should be taken into account; the contribution of this configuration increases with increasing degree of doping, and it becomes dominant at x = 1. In all cases, the manganese state is high-spin.