Atomic migration and ordering phenomena in bulk and thin films of FePd and FePt

Abstract

Order -order" kinetics was studied by means of "in situ" and quasi-residual (REST) resistometry in bulk and thin films of L1 0 -ordered FePd and FePt intermetallics. Substantial effect of magnetic ordering on the activation energy for chemical ordering was revealed in FePd. A discontinuous change of ordering dynamics was detected in FePt between 800 and 830 K. The results are consistent with the data of Fe* diffusion in FePt multilayer examined by means of nuclear resonant scattering in grazing-incidence geometry (GINRS). Monte Carlo (MC) simulations of "order -order" processes in L1 0 -ordered bulk FePd and FePt and nanolayered FePt have been carried out using Glauber dynamics with vacancy mechanism of atomic jumps. Multi-timescale "order -order" relaxations observed in the bulk were predominated in nanolayers by a reorientation of the initial z-variant L1 0 superstructure into a mixture of x-and y-variants. Experimental studies of atomic migration General remarksAtomic migration in the examined L1 0 -ordered intermetallics was studied by considering two sorts of phenomena: "order -order" kinetics controlled by atomic migration in non-steady-state conditions, and self-diffusion showing atomic migration in a steady state.An "order -order" relaxation, the kinetics of which is studied, is a response of a system with the degree of chemical order equilibrated at certain external conditions (temperature, pressure etc.) to a sudden change of these conditions. After such a change, the system evolves towards a state with the degree of chemical order corresponding to thermodynamic equilibrium in the new conditions 1 . R. Kozubski et al.: Atomic migration and ordering phenomena in bulk and thin films of FePd and FePt Z. Metallkd. 97 (2006) 3  Carl Hanser Verlag, München 273 B Basic 1 In "order -order" relaxations, both the initial and the final equilibrium states belong to the domain of chemical long-range order. Zeitschrift für Metallkunde downloaded from www.hanser-elibrary.com by Kungliga Tekniska on August 26, 2015For personal use only.