Ion beam modification of perpendicular magnetic anisotropy in [Co/Pt]_n multilayers and FePt thin films

Abstract

For [Co(3Å)/Pt(10Å)]n multilayers and FePt(111) L10 ordered films exposed to energetic ion beam irradiation, we have experimentally determined the dependence of the perpendicular coercivity on ion dose, for a variety of ion species and energies. A simple model based on ballistic displacement of Co (or Fe) atoms from ordered configurations is presented, which predicts an exponential decline of anisotropy with ion dose. The perpendicular coercivity for these samples is indeed found to decline in this way. The ballistic displacement model, evaluated using SRIM Monte Carlo simulation, roughly reflects the observed dependence on ion species and energy. However, the experimental data would demand a displacement probability per incident ion many times larger than that obtained from SRIM.