Magnetic Properties and Crystallographic Structure of Fe $_{3}$ Pt Thin Films

Fe_100-xPt_x (x = 20, 25, and 30) thin films with nominal thickness 50 nm were prepared by radio-frequency (RF) magnetron sputtering onto glass substrates. Crystallographic structure and magnetic properties of such films were investigated by varying Fe content, annealing temperature (400-700degC), and heating process. Crystallographic structure obtained by X-ray diffraction (XRD) indicated that ordering of L1₂ Fe₃Pt phase takes place for Fe₇₅Pt₂₅ postannealed above 400degC. Ordering parameter of the Fe₇₅Pt₂₅ sample increases from 0.29 to 0.94 as annealing temperature rises from 400degC to 700degC. Saturation magnetization 1270 emu/cm³ was obtained in Fe₇₅Pt₂₅ films annealed at 700degC. Fe₇₀Pt₃₀ films annealed at 700degC show similar characteristics with those of Fe₇₅Pt₂₅, while Fe₈₀Pt₂₀ films exhibit paramagnetism due to disordered Fe-rich face-centered cubic (fcc) structure. Postannealing seems necessary for formation of pure L1₂ Fe₃Pt phase while in situ annealing leads to formation of a metastable tetragonal Fe₃Pt phase, as confirmed by XRD.