Cobalt ferrite/metal composite thin films with a saturation magnetization (Ms) of ∼0.729 Weber m−2 were prepared by a reactive sputtering method. The Ms of the thin films increased with increasing substrate temperature. The microstructures of the thin films were identified by a convergent beam electron diffraction method. For the thin films deposited at high substrate temperatures (>300 °C), CoxFe1-x (x≈0.62) metal alloys were separated from the cobalt ferrite matrix. A cobalt ferrite phase was determined as CoFe2O4 with a cubic structure (a0 = 0.839 nm) and a space group of Fd3m, while a metal phase CoxFe1−x (x≈0.62) with a b.c.c. structure (a0 = 0.289 nm) and a space group of Im3m.