Structural modifications in FexCo1-x/Cu multilayers induced by ion irradiation

The structural evolution of Fe30Co70 /Cu multilayers under ion irradiation is investigated in detail using x-ray techniques. The samples were irradiated with two different ions, 50 keV of He+ and 600 keV of Kr+, at room temperature. No substantial changes were observed after He+ irradiation; the He+ ions promote some disorder in the FeCo layers, an increase of the Cu(111) texture, and grain size. After Kr+ irradiation a structural phase transition from bcc to fcc occurs in the FeCo layers.Avery pronounced increase of the Cu(111) texture and grain size is also observed. According to the equilibrium phase diagrams such fcc phase is not expected for the FeCo alloy at the composition of Fe30Co70. This fcc phase is imposed by the Cu fcc structure of the adjacent layers, which induce the regrowth of the FeCo layers structure from bcc to fcc during the relaxation period of the atomic collision cascades. Also, after the Kr+ irradiation a multilayer structure still persists, as showed by the x-ray reflectivity