Iron self-diffusion in amorphous FeZr/~(57)FeZr multilayers measured by neutron reflectometry

摘要

Self-diffusion of iron in ~(natural)Fe_(67)Zr_(33)/~(57)Fe_(67)Zr33 multilayers has been investigated by neutron reflectometry. The as-deposited multilayer is amorphous in nature. It remains amorphous up to a temperature of 573 K and thereafter nanocrystallizes with an average grain size of 6 nm. The self-diffusion in the multilayers has been measured after isothermal vacuum annealing below the nanocrystallization temperature by monitoring the decay of the intensity of the first order Bragg peak, arising due to the isotopic periodicity. It has been found that the diffusivity at different temperatures follows an Arrhenius-type behavior with the preexponential factor D_0=5 x 10~(-18±1) m~2s~(-1) and the activation energy E=0.38±0.05 eV, respectively. These values of E and D_0 follow the well-known E-D_0 correlation and on the basis of this correlation it is suggested that diffusion mechanism in the present case is not highly collective but involves a rather small group of atoms.