Laser processing of magnetically soft multilayer Ni₈₁Fe₁₉ thin films: Control of anisotropy

We examine the low frequency BH loop and complex permeability spectra of multilayer permalloy films laser processed to define samples consisting of stripes perpendicular and parallel to the as-deposited easy axis. For stripes defined perpendicular to the easy axis, it is found for films of thickness ≥ 0.745 mu;m that the demagnetizing field, which is a function of groove depth and stripe width, is able to reorient the easy and hard axes from the initial orientation resulting in a permeability spectra dependent upon groove depth. For relatively thick spacer layers, 45 nm, laser definition of stripes perpendicular to the easy axis induces the different magnetic layers to switch independently. For thinner films the easy and hard axes do not re-orient, but the independent switching of the layers is seen for the thicker spacer layer films. For stripes defined parallel to the easy axis the anisotropy of the sample increases with groove depth, resulting in a decrease in measured permeability.