Activation volume for nanocrystal growth in amorphous Nd9Fe85B6

We have measured the pressure dependence of the growth of alpha-Fe and Nd2Fe14B nanocrystals in amorphous Nd9Fe85B6 up to 6 GPa at a temperature of 923 K, yielding an activation volume of Delta V*= (0.76 +/- 0.04) and (0.57 +/- 0.05)Omega for atomic diffusion in the growth process of alpha-Fe and Nd2Fe14B nanocrystals, respectively, where Omega 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. (C) 2008 American Institute of Physics. [DOI:10.1063/1.3000565]