Abnormal lattice effect on magnetic/transport phase diagram in La0.7-xLuxSr0.3MnO3 perovskites

An anomalous dependence of the average ion radius [r(A)] on Curie temperature (T-C) and metal-insulator (M-I) transition is obtained in La0.7-xLuxSr0.3MnO3 compared with the phenomenon observed by Hwang [Phys. Rev. Lett. 75, 914 (1995)]. Little variation in T-C is found when xless than or equal to0.4; whereas a sharp drop in T-C only occurs at x>0.4. Meanwhile, the M-I transition occurs at a much lower temperature than T-C when x varies from 0.1 to 0.4. X-ray diffraction patterns show coexistence of rhombohedral and hexagonal lattice symmetry for the Lu-substituted manganites. We suggest that a magnetic inhomogeneity caused by different local distortion of the lattice around La3+ and Lu3+ ions should be responsible for the magnetic/transport abnormality. (C) 2002 American Institute of Physics.Physics, AppliedSCI(E)EI11ARTICLE1210218-102209