Accelerated magnetic re-ordering in Ne+ irradiated FeAl thin films

Thermally activated (re)ordering processes in ferromagnetic Fe60Al40 thin films during in-situ annealing have been investigated by magnetometry and positron annihilation spectroscopy supported with atomic superposition calculations. A ferromagnetic A2-disordered phase coexists with a paramagnetic B2-ordered phase in the as-grown sputter deposited films. Due to thermal treatment at elevated temperature of 773K the B2-phase can be fully established. However, employing Ne+ irradiation as a tool to generate a pure A2-phase and subsequent mild temperature annealing the activation temperature for (re)ordering can be decreased to only 400K. It will be shown that due to immobile large vacancy clusters, which are dominant in the as-grown films and possess a high thermal activation barrier the ordering is strongly hindered.
Ion irradiation breaks down these pinning defects strongly accelerating thermal diffusion and reordering. These results provide insights into thermal reordering processes in binary alloys, and the consequent effect on magnetic behavior.