Magnetic properties and crystallographic structure of [Fe.sub.3]Pt thin films

[Fe.sub.100-x] [Pt.sub.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 (400-700 [degrees]C), and heating process. Crystallographic structure obtained by X-ray diffraction (XRD) indicated that ordering of [L.sub.12] [Fe.sub.3] Pt phase takes place for [Fe.sub.75] [Pt.sub.25] postannealed above 400 [degrees]C. Ordering parameter of the [Fe.sub.75] [Pt.sub.25] sample increases from 0.29 to 0.94 as annealing temperature rises from 400 [degrees]C to 700 [degrees] C. Saturation magnetization 1270 emu/[cm.sup.3] was obtained in [Fe.sub.75] [Pt.sub.25] films annealed at 700 [degrees]C. [Fe.sub.70] [Pt.sub.30] films annealed at 700 [degrees]C show similar characteristics with those of [Fe.sub.75] [Pt.sub.25], while [Fe.sub.80] [Pt.sub.20] films exhibit paramagnetism due to disordered Fe-rich face-centered cubic (fcc) structure. Postannealing seems necessary for formation of pure [L1.sub.2] [Fe.sub.3] Pt phase while in situ annealing leads to formation of a metastable tetragonal [Fe.sub.3] Pt phase, as confirmed by XRD. Index Terms--Coercivity, [Fe.sub.3] Pt thin films, [L1.sub.2] superlattice, metastable phase, phase transformation, saturation magnetization.