On the structural and magnetoelectrical characterization of epitaxial SrRuO3 thin films grown on (001) SrTiO3 substrates

High-quality epitaxial thin films of the ferromagnetic metallic oxide SrRuO3 (SRO) were fabricated by dc-sputtering at high oxygen pressure and their structural and magnetoelectrical properties were carefully studied. The films featured a Curie temperature T-C similar to 160 K and a magnetic moment of similar to 0.7 mu(B) per Ru ion. The temperature dependent magnetization could be well described by the scaling relation M(T) proportional to (T-C - T)(beta) with a critical exponent beta = 0.53 over the entire ferromagnetic temperature range. A negative magnetoresistance, MR, on the order of a few percent was found up to room temperature. MR showed a maximum of similar to 4% right at T-C where a kink structure of the resistivity, rho, at zero field was flattened out on magnetic field application. This rho contribution could be related to scattering due to orientational disorder of the Ru magnetic moments which become aligned by an external magnetic field. In addition, an equally strong MR effect, related to localization phenomena, could be observed at lower temperature. Particularly, the second MR peak at similar to 35 K might be related to a Fermi-liquid to non-Fermi-liquid crossover. A scaling behavior d rho/dT proportional to vertical bar T - T-C vertical bar(alpha) was observed only above T-C. Here, values for the exponent alpha approximate to -0.4 and alpha approximate to -1.4 were obtained in zero field and in a field of 9 T, respectively. The commonly observed rho minimum, appearing at low temperatures (similar to 3 K in the present case), is correlated with the structural disorder of the SRO films and is believed to have its origin in quantum corrections to the conductivity (QCC). (C) 2008 Elsevier Masson SAS. All rights reserved.