Effect of the cation size disorder on charge ordering in rare-earth manganates

Abstract

The effect of disorder arising from the mismatch between the average sizes of the A-site cations in the rare-earth manganates, L_0.5A_0.5MnO₃ (L=rare earth, A=alkaline earth), on their charge-ordering behavior has been investigated. Measurements on two series of manganates with a fixed average cation radius, <r_A>, of 1.17 and 1.24 Å, reveal that the charge-ordering transition temperature, T_CO, is not very sensitive to the size mismatch unlike ferromagnetic T_C or metal-insulator transition data. Furthermore, T_CO is not affected greatly by the orthorhombic lattice distortion. The observed decrease in T_CO with increase in <r_A> is consistent with a quadratic dependence upon (r_A⁰-<r_A>) where r_A⁰=1.13Å.