Ion-Beam Bombarded SiO_2 Layer Effects on the Microstructure and Magnetism in FePt/SiO_2 Bilayers

摘要

We have shown that the structural and magnetic properties of FePt thin films were affected strongly by capped SiO_2 layers prepared by ion-beam bombardment followed by post-annealing. Compared to the single fcc FePt phase in the as-deposited FePt/SiO_2 bilayer (0% O_2/Ar), annealing at 550 ℃ produced an ordered L1_0 FePt phase with enhanced coercivity (～14 kOe). Increasing the %O_2/Ar during deposition of the top SiO_2 layer resulted in smaller ordered FePt grains separated by grain boundaries of SiO_2. We find that the (001) diffraction peak is broadened considerably with larger SiO_2 deposition %O_2/Ar and annealing, likely due to the induced strain. Our results indicate that FePt/ SiO_2 films deposited with lower %O_2/Ar, the oxygen atoms created by the ion-beam bombardment act effectively to inhibit the FePt grain growth, whereas the excess oxygen atoms present during film deposition with higher %O_2/Ar may induce a local strain on the FePt crystallites by occupying the interstitial sites in the FePt lattice.