Magnetoresistance of La1-xSrxMnO3 films deposited by RF magnetron co-sputtering

La-Sr-Mn-O thin films have been grown on SiO2/Si(1 0 0) and MgO(1 0 0) substrate by co-sputtering LSMO compound target and pure Sr target. The La-Sr-Mn-O films deposited on MgO were grown to single phase, while the films grown on SiO2/Si showed polycrystalline structure. The Sr ratio x of the deposited La1-xSrxMnO3 films could be controlled in the range of 0.15 and 0.23 by varying the RF power to the Sr target. For the films on MgO(1 0 0), metal-insulator transition occurred at 270 K for x=0.15 and transition temperature increased as the Sr ratio increased. The MR curves showed sharp peaks at a temperature slightly lower than TM-I. The maximum MR reached about 46.4% at 250 K for 1.5 T. For the films on SiO2, the MR decreased monotonically, and films did not show any Sr ratio dependent electrical property differences