Effect of substitution of Mn³⁺ by Ni³⁺ and Co³⁺ on the charge-ordered states of the rare earth manganates, Ln_0.5A_0.5MnO₃

Abstract

Substitution of Mn³⁺ in Nd_0.5Sr_0.5MnO₃ by Ni³⁺ and Co³⁺ upto 5% destroys the charge-ordered (CO) state and renders the material ferromagnetic and metallic. In Nd_0.5Ca_0.5MnO₃, the charge-ordering transition temperature, T_CO, decreases with increase in the Ni³⁺ or Co³⁺ content and the ferromagnetic metallic state occurs below T_CO. Substitution of Ni³⁺ or Co³⁺ has no effect on the CO state of Y_0.5Ca_0.5MnO₃, showing thereby that such substitution effects delineate the different types of CO states caused by differences in the average size of the A-site ions. The presence of empty e_g orbitals in the substituent transition metal ion appears to be necessary for destroying the CO state in these manganates.