Abstract: The influence of Dy doping at La-site on transport properties of La_0.7-xDy_xSr_0.3MnO₃
(x=0.00, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, and 0.70) was studied. The experimental results indicate that with increasing Dy doping, the system
undergoes a transition from long range ferromagnetic order to the cluster-spin glass state and further to antiferromagnetic order. The transport properties
exhibit abnormal behaviour at high doping condition. For x=0.50, a transition from metal to insulator occurs after the occurrence of
insulator-metal transition near T_c, which seldom occurs in ABO₃ structure. The samples of x=0.60 and 0.70, exhibit insulator behavior far
above T_c.

Key words: magnetic structure, transport properties, colossal magnetoresistance effect