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Understanding the L10 phase transformation of FePt nanocrystals in FePt:X (X = nonmagnetic materials) nanocomposite thin films is of particular importance for controlling and designing these films as ultrahigh density magnetic recording media. In this study, by employing temperature- and pressure-dependence of the rate constant of phase transition, the nucleation (En = 0.3 eV) and growth (Eg = 0.9 eV) activation energies of L10 ordered domains, as well as an activation volume ΔV* ≈ 0.96 Ω (Ω = average atomic volume) for L10 ordering transition in FePt:Ag nanocomposite thin films have been successfully determined. These data suggest that the growth of L10 ordered domains is predominantly dependent on the diffusion of Fe atoms in FePt crystals, and that the diffusion of Ag atoms out of FePt lattice prompts the nucleation of the L10 ordered domains. These findings have a direct implication for designing FePt:Ag nanocomposite thin films with high pack fraction of L10-FePt nanocrystals. [ABSTRACT FROM AUTHOR]

We have measured the pressure dependence of the growth of α-Fe and Nd2Fe14B nanocrystals in amorphous Nd9Fe85B6 up to 6 GPa at a temperature of 923 K, yielding an activation volume of ΔV*=(0.76±0.04) and (0.57±0.05)Ω for atomic diffusion in the growth process of α-Fe and Nd2Fe14B nanocrystals, respectively, where Ω is the mean atomic volume of the alloy. This demonstrates that the growth of nanocrystals is dependent on atomic diffusion mediated by vacancy-type thermal defects. Atomic processes of the growth of nanocrystals are discussed. [ABSTRACT FROM AUTHOR]

We have measured the pressure dependence of the growth of α-Fe and Nd2Fe14B nanocrystals in amorphous Nd9Fe85B6 up to 6 GPa at a temperature of 923 K, yielding an activation volume of ΔV*=(0.76±0.04) and (0.57±0.05)Ω for atomic diffusion in the growth process of α-Fe and Nd2Fe14B nanocrystals, respectively, where Ω is the mean atomic volume of the alloy. This demonstrates that the growth of nanocrystals is dependent on atomic diffusion mediated by vacancy-type thermal defects. Atomic processes of the growth of nanocrystals are discussed. [ABSTRACT FROM AUTHOR]