Effects of growing conditions on the electric and magnetic properties of strained La_2/3Sr_1/3MnO₃ thin films

We investigate the growing condition dependences of magnetic and electric properties of the La_2/3Sr_1/3MnO₃ thin films grown on SrTiO₃ (001) substrates. With reducing the film thickness and growth pressure, the Curie temperature (T_C) drops off, and the magnetism and metallicity are suppressed. At an appropriate deposition temperature, we can obtain the best texture and remarkably enhance the magnetic and electrical properties. However, the resistivity of film cannot be modulated by changing the dc current and green light intensity. This result may be induced by the coherent strains in the epitaxially grown film due to its lattice mismatching that of the SrTiO₃ substrate. Furthermore, we show that the relations between the magnetism and the resistivity for the typical films with different thickness values. For the 13.4-nm-thick film, the R-T curve presents two transition behaviors: insulator-to-metal and metal-to-insulator in the cooling process: the former corresponds to magnetic transition, and the later correlates with thermal excitation conduction.