•Fe100-xPtx alloy films are prepared by ion beam sputtering technique.•Composition was tuned by precise control of exposed area of Fe and Pt to ion beam.•Chemical composition films are confirmed via × ray fluorescence and reflectivity.•Degree and type of chemical ordering is revealed via grazing incidence XRD. Fe100-xPtx alloy films are fabricated by controlled ion beam sputtering. Composition of the films was tuned by varying the relative atomic percentage of iron and platinum via controlling the area exposed to the ion beam. Structural and magnetic properties of films are studied using x-ray reflectivity, x- ray fluorescence, x-ray diffraction and Magneto Optic Kerr Effect. Isochronal annealing of films was done at 500 °C for 1 hour. Evolution of L10 ordering upon thermal annealing is investigated and correlation with the relative atomic percentage has been observed and explained. The finding of the work is useful for the fabricating the future recording media material.