Hard magnetic L10 FePt thin films and nanopatterns

L10Fe54Pt46 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 μ0Hc. Arrays of square L10Fe54Pt46 nanodots covering 3mmx3mm were produced using electron beam lithography. Post-annealing at high temperatures such as 8000C 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