The large magnetoresistance of La_1-xSr_xCoO₃ at low temperatures

We report here the resistivity ( rho ) and the magnetoresistance (MR) of the ferromagnetic perovskite oxide system La_1-xSr_xCoO₃ (0.1<x<0.5) in a temperature range down to 4.2 K and magnetic fields up to 6 T. The MR is positive for x=0.5 and is negative for x<or=0.4. We find that while in the metallic samples (x>0.2) the magnitude of the MR is typically small (<10%), it is large in the composition range where x<or=0.2, where the system is close to the metal-to-insulator transition. We compare these observations with those made for the La_1-xSr_xMnO₃ system.