Reduction of grain size and ordering temperature in L10 FePt thin films

In this research, a more effective procedure for reducing the ordering temperature of the L1₀ FePt thin films is proposed. These thin films, with thickness varying from 10 nm to 200 nm, are prepared by conventional magnetron sputtering system with a dc power supply and then postannealed in vacuum. The phases and microstructures of the films are characterized by X-ray diffraction (XRD) with Cu-Kα radiation and transmission electron microscopy (TEM) bright field image, respectively. TEM bright field images show that the films have average grain sizes of about 6 nm. XRD patterns show that there is no evidence that ordered structure exists in the film when annealing temperature (T_an) ≤ 300°C. For T_an ≥ 350°C, the disordered fcc FePt phase transforms into the ordered L1₀ FePt phase. Vacancies into the film are formed easily due to the high deposition rate process in this investigation. Some extra energy is introduced into the as-deposited film during deposition and reduced the order-disorder energy barrier.