Hard magnetic L10L10 FePt thin films and nanopatterns

L10L10Fe54Pt46Fe54Pt46 thin films were prepared on MgO(0 0 1) single crystal substrates by ion beam sputter deposition and post-annealing in Ar atmosphere. The influence of annealing temperature, film thickness and an Au buffer layer on the magnetic properties was investigated. Films with thicknesses d<20nm exhibit an out-of-plane texture, whereas films with d⩾20nm show an isotropic magnetization behavior. An Au buffer layer leads to a dewetting of the substrate surface during annealing resulting in the formation of isolated single-domain particles for film thicknesses d⩽20nm. The island-like films show a significant increase of the coercivity μ0Hcμ0Hc. Arrays of square L10L10Fe54Pt46Fe54Pt46 nanodots covering 3mm×3mm were produced using electron beam lithography. Post-annealing at high temperatures such as 800∘C changes the shape of the squares. For small dot thicknesses as 20 nm the nanodots split into an accumulation of isolated particles of irregular shape which yield a high out-of-plane coercivity of μ0Hc=2.35T. When the dot size is reduced, the fraction of the hard magnetic phase decreases.