THE LARGE MAGNETORESISTANCE OF LA1-XSRXCOO3 AT LOW-TEMPERATURES

We report here the resistivity (rho) and the magnetoresistance (MR) of the ferromagnetic perovskite oxide system La1-xSrxCoO3 (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 less than or equal to 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 less than or equal to 0.2, where the system is close to the metal-to-insulator transition. We compare these observations with those made for the La1-xSrxMnO3 system.