On the structural and magnetoelectrical characterization of epitaxial SrRuO 3 thin films grown on (001) SrTiO 3 substrates

Abstract

High-quality epitaxial thin films of the ferromagnetic metallic oxide SrRuO 3 (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 ∼ 160 K and a magnetic moment of ∼0.7 μ B per Ru ion. The temperature dependent magnetization could be well described by the scaling relation M( T) ∝ ( T C − T) β with a critical exponent β = 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 ∼4% right at T C where a kink structure of the resistivity, ρ, at zero field was flattened out on magnetic field application. This ρ 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 ∼35 K might be related to a Fermi-liquid to non-Fermi-liquid crossover. A scaling behavior d ρ/d T ∝ | T − T C| α was observed only above T C. Here, values for the exponent α ≈ −0.4 and α ≈ −1.4 were obtained in zero field and in a field of 9 T, respectively. The commonly observed ρ minimum, appearing at low temperatures (∼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).