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

From a Monte Carlo study of the ferromagnetic Kondo lattice model for doped manganites, including the antiferromagnetic superexchange interaction (J(A F)) we found that the ferromagnetic ordering was suppressed as J(AF) increa sed. The ferromagnetic transition temperature T-c, as obtained from a mean- field fit to the calculated susceptibilities, was found to decrease monoton ically with increasing J(AF). Further, the suppression in T-c scales with t he bandwidth narrowing induced by the antiferromagnetic frustration origina ting from J(AF) From these results, we propose that the change in the super exchange 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 m anganites of the type (La0.7-yPry)Ca0.3MnO3.