Effect of R on the magnetic transition temperature of RMn0.5Co0.5O3

Abstract The effect of R on the ferromagnetic Curie temperatures of two different phases of RMn 0.5 Co 0.5 O 3 (R=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) has been studied. For both high- T c and low- T c phases of RMn 0.5 Co 0.5 O 3 , T c decreases with decreasing ionic radius of R 3+ and the tolerance factor. The rate of decrease of T c is larger for the high- T c phases containing Mn 3+ and low-spin Co 3+ when compared to the low- T c phases containing Mn 4+ and Co 2+ , indicating that the Mn 3+ –O–Mn 3+ superexchange interactions are more susceptible to internal pressure effect of R 3+ when compared to the effect on the Mn 4+ –O–Co 2+ superexchange interactions.