Structure and electrical properties of epitaxial SrRuO₃ thin films controlled by oxygen partial pressure

SrRuO₃ (SRO) thin films have been grown on (001)-oriented SrTiO₃ substrate under various oxygen partial pressures (P_O2). A typical step-and-terrace surface morphology and coherent epitaxy characteristics are found in the SRO films for high oxygen pressure growth (P_O2 ≥ 10 Pa). Under such high P_O2, SRO films exhibit metallic behavior over a temperature range of 10 K ≤ T ≤ 300 K. A detailed study on the transport properties of the metallic SRO films reveals that the resistivity (ρ) follows the law ρ(T)-ρ₀ ∝ T^x (x = 0.5, 1.5, or 2). Below ferromagnetic transition temperature (T_c), ρ(T) follows T² dependence below 30 K and T^1.5 dependence at T > 30 K, respectively. This result demonstrates that a transition between the Fermi-liquid (FL) and non-Fermi-liquid (NFL) behavior occurs at ∼30 K. Furthermore, ρ(T) follows T^0.5 dependence at T > T_c in the paramagnetic metal state. We have found that the FL to NFL transitions as well as the ferromagnetic transition are corresponding to the abnormal peaks in the magnetoresistance curves, suggesting the coupling of electronic and magnetic properties. The transition temperature of FL to NFL for metallic SRO films is almost independent on P_O2, while T_c slightly increases with P_O2.