Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu_1 - x Fe _x O_3 - δ Thin Films

Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu_1 - x Fe _x O_3 - δ epitaxial thin films (x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu_1 - x Fe _x O_3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR (~36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies (δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr_1 - x La _x )(Ru_1 - x Fe _x )O₃. These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu_1 - x Fe _x O_3 - δ thin films.