Transport and Magnetic Properties of La1-xSrxMnO3 Films

A magnetron dc sputtering system is used to deposit La_0.7Sr_0.3MnO₃ films onto quartz and SrTiO₃(001) substrates. The Curie temperature T_c of LSMO films on both substrates is around 365 K. The temperature dependent resistance of the LSMO/STO film exhibits a semiconductor-metal transition at T_p around 365 K, which coincides with the T_t. However, for the LSMO/quartz film, T_p is 210 K. By investigating the surface morphology of the LSMO films on these two substrates, a granular structure was observed for the LSMO/quartz film but not for the LSMO/STO film. It is suggested that the granular structure is crucial to the difference between T_p and T_c.