Anomaly of magnetization under the structural phase transition in La0.7Ca0.165Sr0.135MnO3 manganite

A study of crystal structure and magnetization of La0.7Ca0.3−xSrxMnO3 lanthanum manganites (0.105⩽x⩽0.18) is presented. At room temperature the x=0.105, 0.12 and 0.135 samples were orthorhombic Pbnm phase, and x=0.15, 0.165 and 0.18 compositions were rhombohedral R3¯c phase. The magnetization on temperature dependence, M=M(T), for the samples (except x=0.135) showed usual (without any “kink”) behaviour. The M=M(T) curve for the x=0.135 sample revealed two-step dependence with the inflexion points at 309 and 320 K. The effect is explained by a supposition that the temperatures are the Curie points of Pbnm and R3¯c phases, respectively, and caused by the structural orthorhombic-rhombohedral phase transition observed in the sample at the above temperature interval.