Suppression of ferromagnetic ordering in doped manganites: Effects of the superexchange interaction

Abstract

From a Monte Carlo study of the ferromagnetic Kondo lattice model for doped manganites, including the antiferromagnetic superexchange interaction ${(J}_{\mathrm{AF}}),$ we found that the ferromagnetic ordering was suppressed as ${J}_{\mathrm{AF}}$ increased. The ferromagnetic transition temperature ${T}_{c},$ as obtained from a mean-field fit to the calculated susceptibilities, was found to decrease monotonically with increasing ${J}_{\mathrm{AF}}.$ Further, the suppression in ${T}_{c}$ scales with the bandwidth narrowing induced by the antiferromagnetic frustration originating from ${J}_{\mathrm{AF}}.$ From these results, we propose that the change in the superexchange interaction strength between the ${t}_{2g}$ electrons of the Mn ions is one of the mechanisms responsible for the suppression in ${T}_{c}$ observed in manganites of the type $({\mathrm{La}}_{0.7\ensuremath{-}y}{\mathrm{Pr}}_{y}){\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}.$