[en] L1₀ ordered FePt alloy films with perpendicular magnetic anisotropy have been prepared by alternating Fe (001) and Pt (001) monatomic layers on MgO (001) substrates at low temperatures below 300 deg. C. In addition to molecular beam epitaxy (MBE) technique reported so far, ultra high vacuum compatible dc magnetron sputtering was used for the sample preparation, and the properties for sputtered films are compared with those for MBE films. When the Ar gas pressure during sputtering is equal to or higher than 5 mTorr, sharp (001) and (003) superlattice peaks have been observed in the x-ray diffraction (XRD) patterns, and the magnetization measurements show that the films are perpendicularly magnetized. However, the uniaxial anisotropy energy K_u for sputtered films is smaller than that for MBE films even when the long range order parameter estimated from the intensity ratio of the superlattice to fundamental XRD peaks is almost the same in both cases