Sputter erosion of ferromagnetic thin films

We investigated the effects of sputter erosion of iron thin films grown on silica and silicon substrates by electron beam evaporation. Iron thin films with typical thickness of 100 nm were sputter eroded using Xe ions with energies of 4 keV up to 450 keV, substrate temperatures of 100 K and 300 K, ion fluences up to 1 × 1017 ions /cm2 and angles of incidence to the surface normal varied between 0° and 80°. The surface topography was monitored by atomic force microscopy and the magnetic properties of the near-surface region were monitored using magneto optical Kerr effect. The as-deposited nanocrystalline films have an rms roughness of 1 nm and are magnetically almost isotropic. After sputter erosion the rms roughness increases up to 3 nm, depending on the irradiation parameters, and the films become magnetically softer. We observe ripple formation with orientation parallel to the direction of the incident ion beam, as well as uniaxial magnetic anisotropy, for ion irradiation at incidence angles of 80°.