Deterioration in coercivities of Fe–Pt and Co–Pt thin film magnets by ion irradiations

Abstract Iron–platinum and cobalt–platinum thin film magnets with thicknesses of 120 nm and 135 nm, respectively are irradiated with 180 keV 20 Ne or 2 MeV 4 He ions, and in-plane coercivities of the magnets are measured as a function of fluences of the ions. Densities of displaced Fe, Co and Pt atoms are calculated with a TRIM code. It is found that the coercivities are determined by the densities of displaced atoms rather than the kind of ions and incident energies. Resistance of the Co–Pt thin film magnets to irradiation of 2 MeV 4 He ions is almost the same as that of the Fe–Pt magnets.