Enhanced magnetic properties of annealed Fe₄₈Pt₅₂C composite films by N incorporation

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N‐incorporated Fe 48 Pt 52 C composite films were fabricated using a reactive facing‐target sputtering system in a mixture of Ar and N 2 gases, and annealed in a chamber with the vacuum of 10 −6 Pa. Upon annealing, the escape of N atoms improves the ordering of the face‐centered tetragonal (fct) FePt grains. The coercivity of the 100‐nm thick films increases with the increase of nitrogen partial pressure. The maximum coercivity reaches 7.2 kOe at a 10‐kOe field, and the reversal mechanism approaches the Stoner–Wohlfarth (S–W) rotation mode. The easy axis turns from perpendicular to parallel to the film plane, and the coercivity increases with the increase of the film thickness ( t ). With increasing t , the out‐of‐plane magnetization decreases, but the in‐plane magnetization first increases, then decreases. The change of the magnetic properties should be related to the escape of the N atoms and the lattice mismatch effect of the MgO(100) substrates.