Atomic migration on ordering and diffusion in bulk and nanostructured FePt intermetallic

"Order-order" kinetics was studied by means of in situ and quasi-residual resistometry in bulk polycrystal stoichiometric L1 0-ordered FePt and in epitaxially deposited FePt thin Film. In addition, Fe diffusion in FePt thin film was examined by means of a combination of nuclear resonant scattering and nuclear tracer techniques. In bulk FePt, a discontinuous drop of the activation energy for chemical ordering (from 2.7-15 eV) was detected below 850 K, definitely away from the Curie point (735 K). The activation energy for Fe radiotracer diffusion in the FePt thin film studied below 900 K was found to be equal to 1.7 eV (in view of the value higher than 3 eV measured above 1100 K). Kinetic Monte Carlo simulations of order-order processes in bulk and nanolayered FePt reproduced their experimentally observed multi-time-scale character. In simulated FePt nanolayers, a reorientation of the initial z-variant L10 superstructure into a mixture of x and y variants was definitely a dominating process. ΠASM International.