Morphological change in FePt nanogranular films induced by irradiation with 100Â keV He ions

We have investigated the effects of He-ion irradiation on structures of FePt nanoparticles dispersed in thin films with amorphous Al2O3 matrix. The coarsening of FePt nanoparticles is suppressed under irradiation with 100 keV He+ ions at an elevated temperature, such as 923 K. The delay of particle growth is also recognized in the post-irradiation annealing. On the other hand, He-irradiation is of little assistance in promoting L10 ordering in the nanogranular films at a temperature as low as 573 K.