Transport properties in La0.7-xGdxSr0.3MnO3 system

The influence of Gd doping at La-site on the electrical transport properties and the co-lossal magnetoresistance of LaGdSrMnO（x=0.00,0.10,0.15,0.20,0.30,0.40,0.50,0.60,and 0.70）is studied.The experimental results indicate that the transport properties exhibit abnor-mal behavior under high doping condition.For x=0.50,we find that a transition from metal to in-sulator occurs after the occurrence of insulator-metal transition near To,which seldom occurs inABOstructure.For samples x=0.60 and 0.70,it exhibits insulator behavior far above T.Theseabnormal behaviors are attributed to different magnetic background,i.e.the system undergoes atransition from long range ferromagnetic order to the cluster-spin glass state and further toantiferromagnetic order.