Phase diagram and anomalous properties of La0.7M0.3MnO3 lanthanum manganites near the structural phase transition

The La0.7Ca0.3-xBaxMnO3 (x=0; 0.03; 0.06...0.3) and La0.7Ca0.3-xSrxMnO3 (x=0.105, 0.12, 0.135, 0.15, 0.165, and 0.18) lanthanum manganites were synthesized and studied. The Curie temperature T-C of Ba range showed a sharp change near the concentration structural orthorhombic-rhombohedral phase transition. The T-C values for that range are under the "classical" ferromagnetic-paramagnetic line. The T-C temperatures of Sr range of samples are independent on x value at the vicinity of structural transition in the rhombohedral phase. Temperature dependence of magnetization of the La0.7Ca0.165Sr0.135MnO3 composition looks like a two-step curve which is caused by the closeness of ferromagnetic ordering and structural phase transition temperatures. (C) 2002 American Institute of Physics.