Effect of internal pressure on charge-ordered rare earth manganates

Abstract

The effect of internal pressure on charge-ordered rare earth manganates of the composition Ln_1−xA_xMnO₃ (Ln=La, Pr, Nd and A=Ca, Sr) has been studied by varying the average radius of the A site cations (<r_A>). Increasing <r_A> is generally accompanied by an increase in the ferromagnetic transition temperature and a decrease in the charge-ordering transition temperature. On increasing the size of the Asite cations by appropriate substitution, charge-ordered insulators such as Pr_0.7Ca_0.3MnO₃and Nd_0.5Ca_0.5MnO₃ become ferromagnetic, accompanied by an insulator-metal transition. In Pr_0.5Sr_0.5MnO₃, substitution of La in place of Pr destroys the antiferromagnetic transition and favors the ferromagnetic metallic state.