Fe50Pt50 nanodots dispersed in a SiO2 film (Fe50Pt50 nanodot film) were formed by a self-assembled nanodot deposition (SAND) method in which Fe50Pt50 and SiO2 are cosputtered in a high vacuum rf magnetron sputtering equipment. Fe50Pt50 pellets are laid on a SiO2 target in a sputtering chamber to form the Fe50Pt50 nanodot film in the SAND method. The size and density of Fe50Pt50 nanodot were controlled by changing the ratio of the total area of Fe50Pt50 pellets to that of SiO2 target. The Fe50Pt50 nanodot size decreases and its density increases when the ratio decreases. As-deposited Fe50Pt50 nanodots self-assembled to a face-centered-cubic phase of single-crystal structure. The Fe50Pt50 nanodot films were annealed to evaluate the nanodot size controllability, the magnetic anisotropy, and the thermal stability. Fully ordered L10 face-centered-tetragonal Fe50Pt50 nanodots with high magnetocrystalline anisotropy (Ku- - x2245;8.7×107 ergs/cm3) were obtained by in situ annealing at 600 °C for 1 h in a high vacuum ambience. Furthermore, the Fe50Pt50 nanodot film with a monolayer of Fe50Pt50 nanodots was formed by annealing at 800 °C due to the agglomeration of Fe50Pt50 nanodots in the SiO2 film.