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

Abstract

SrRuO3 (SRO) thin films have been grown on (001)-oriented SrTiO3 substrate under various oxygen partial pressures (PO2). A typical step-and-terrace surface morphology and coherent epitaxy characteristics are found in the SRO films for high oxygen pressure growth (PO2 ≥ 10 Pa). Under such high PO2, 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 ∝ Tx (x = 0.5, 1.5, or 2). Below ferromagnetic transition temperature (Tc), ρ(T) follows T2 dependence below 30 K and T1.5 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 T0.5 dependence at T > Tc 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 PO2, while Tc slightly increases with PO2.