Effect of A-site cation substitution on magnetic transition temperature of (LaCa) MnO3.

The ferromagnetic transition temperatures have been measured on two bathes of perovskite manganese oxides such as (La_{1- x} R _x )_2/3Ca_1/3MnO₃(R=Ce, Pr, Nd, etc.) and La_2/3(Ca_{1- y} Cd _y )_1/3MnO₃. It is found that the (La_{1- x} R _x )_2/3Ca_1/3MnO₃ samples have obviously different Curie temperature T _C although their (r_A) (the average A-site cation radius) are almost identical, and the T _C in the system of (La_{1- x} R _x )_2/3Ca_1/3MnO₃(R=Ce, Pr, Nd, etc.) and La_2/3(Ca_{1- y} Cd _y )_1/3MnO₃. It is found that the (La_{1- x} R _x )_2/3Ca_1/3MnO₃ compounds increases with increasing y although (r_A) decreases slightly. It is suggested that the Curie temperature should be influenced by the average local A-site magnetic moment in the ferromagnetic perovskite manganite system. [ABSTRACT FROM AUTHOR]