| Ion-beam sputtering has been used to achieve the growth of FePt thin films and C/FePt granular multilayers at room temperature. The effects of thermal annealing on the structural and magnetic properties has been investigated by transmission electron microscopy, Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, grazing incidence small-angle X-ray scattering, and magnetization measurements. The as-deposited films and granular multilayers show FePt grains (10-20 nm and 2-3 nm in size, respectively) with a disordered face-centered-cubic structure and are magnetically soft. Thermal annealing at temperatures below 650 °C causes partial L10 ordering and growth of the FePt grains to 100-200 nm in the FePt films and to 5-8 nm in the C/FePt multilayers. Thermal annealing of the granular multilayers at 800 °C also results in the preferential graphitization of the carbon matrix and chemical interaction of the Fe atoms with the Si substrate. Magnetization measurements indicate that magnetic hardening occurs after annealing and that the saturation magnetization of the granular multilayers is strongly dependent on the annealing temperature. |
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