Quantitative determination of mixed anisotropies in Fe(100) thin films and annealing-induced magnetic reorientation

A specific formalism for quantification of magnetic anisotropies using transverse biased initial susceptibility measurements in systems with mixed in-plane biaxial and uniaxial anisotropies has been developed, This formalism has been applied to the study of magnetic anisotropies in epitaxial, partially nitrided Fe thin films that exhibit these coexisting anisotropies. The influence of annealing on the structure and magnetic anisotropies in this system is also studied. A restructurating of N into the Fe lattice with the formation of a nonstoichiometric FeN phase is found after sufficient annealing time. An additional result is a 5degrees in-plane rotation of the uniaxial anisotropy direction with respect to the as-grown sample, with no reorientation of the film crystal lattice with respect to the substrate. Possible mechanisms to explain the origin of magnetic anisotropy and the rotation upon annealing of the uniaxial anisotropy are proposed.