Abstract: The magnetic behavior and the transport behavior of La_0.67-xSm_xSr_0.33MnO₃ (x=0.00, 0.10, 0.20, 0.30,0.40, 0.50 and 0.60) systems were studied through measuring the M-T curves, electron spin resonance (ESR)curves and ρ-T curves.The samples exhibit a long-range ferromagnetic order when x = 0.00, 0.10, a cluster-spin glass state when x = 0.20 and 0.30, and an anti-ferromagnetic state at low temperatures when x = 0.40, 0.50 and 0.60.The samples of x = 0.30 and 0.40 show phase separation at temperatures above T_c.The transport behavior of the sample of x = 0.60 becomes abnormal when the doping is high, and an insulator-metal transition occurs near T_c and then a metal-insulator transition occurs, which rarely appears in an ABO₃ structure.It is concludedthat the magnetic and electric behavior changes of the systems depend on the extra magnetism and lattice distortion effect induced by Sm doping.

Key words: Magnetic structure, Phase separation, Transport behavior, Colossal magnetoresistance effect