Interface modification of Fe/Cr/Al magnetic multilayer by swift heavy ion irradiation

Abstract

Interface mixing in [Fe/Cr/Al]x10 multilayer is studied under 120 MeV Ag9+swift heavy ions (SHIs) irradiation. The multilayers with different thicknesses were deposited using electron beam evaporation technique. The SHIs induced modifications in structural and magnetic properties were examined with X-ray reflectivity (XRR), magneto-optic Kerr effect (MOKE), and X-ray absorption fine structure (XAFS) to reveal interface diffusivity, including variation in magnetic coercivity, in-plane anisotropy, and local structure. The height of 1st order Bragg peak of XRR is used to determine the diffusion length as a function of ion fluence, and it is evident that the lower thickness of [Fe/Cr/Al]x10 multilayer possesses higher interface mixing as compared to samples with higher thickness. MOKE results confirm that both multilayers are soft magnetic in nature and show different behavior of in-plane anisotropy. With the SHIs irradiation, coercivity exhibits opposite trends for different thicknesses of Fe/Cr/Al multilayers due to different interface mixing. Fe K-edge XAFS is used for quantitative analysis of the Fe-Cr and Fe-Al phases as a function of multilayer thickness and ion fluence. The inelastic thermal spike (i-TS) model with size effect is used to explain the observed thickness-dependent intermixing due to the SHIs irradiation. The lattice temperature evaluation calculated by i-TS model shows longer spike duration in thinner film resulting in higher mixing.