Spin-polarized current effects in disordered La0.7Ba0.3MnO3 half-metal thin films

We have investigated by means of noise spectroscopy the transport properties of half-metal La0.7Ba0.3MnO3 (LBMO) thin films deposited on MgO substrates. A reduced metal-insulator transition temperature and a peculiar noise behaviour are observed in the films grown on MgO substrates, when compared with similar films grown on SrTiO3 substrates. In particular, a large increase in noise is observed below the metal-insulator transition temperature, associated with a current induced reduction in the excess noise level. This finding is explained in terms of the spin torque effect between regions with depressed Curie temperatures among the ferromagnetic metallic domains. The proposed theoretical model, taking into account the half-metal character of manganites, describes well the experimental data.