[en] SrRu_1−xFe_xO_3−δ (x = 0.00, 0.05, 0.10, and 0.20) thin films were fabricated to study the intrinsic aspects of a “self spin valve”. Using epitaxial strain and high oxygen partial pressure during thin film growth, single phase thin films with negligible oxygen vacancies were successfully grown, and problems related to A-site disorder and grain boundaries were minimized. Under application of an external magnetic field of up to 9 T, the resistivity of all films decreased, resulting in large negative magnetoresistance (up to ∼14.4%), which was stronger at temperatures in the range 10–30 K. An abrupt metal-insulator transition at T∼ 43 K was found in the x = 0.20 film, which was explained using a two-fluid model related to electron–electron interactions. From the model, two fitting parameters were found to be necessary for in-situ and homogenous defects, while three or unphysical fitting parameters were necessary for ex-situ and inhomogeneous defects. - Highlights: • Growth of SrRu_1−xFe_xO_3−δ film without A-site disorder and grain boundary problem. • Intrinsic nature of “self spin valve” observed in SrRu_1−xFe_xO_3−δ film. • Two different nature of metal-insulator transition was found in SrRu_1−xFe_xO_3−δ. • Magnetoresistance up to ∼14.4% were found in SrRu_1−xFe_xO_3−δ in low temperature. • Antiferromagnetic bonding increases with Fe doping concentration.