Determination of the distribution of transverse magnetic anisotropy in thin films from the second harmonic of Kerr signal

We describe a method to determine the magnetic anisotropy distribution in thin films based on Kerr magnetometry, well adapted for single micro- and nanostructures. When the sample is excited by an ac field of small amplitude, for each value of a longitudinal dc field H, the second harmonic of the Kerr signal gives the contribution of the corresponding transverse anisotropy field Hk=H to the anisotropy distribution. The method is tested on a Permalloy-based multilayer microstructure, revealing two anisotropy contributions, one of them deviated from the perfect transverse direction. This confirms and extends a previous characterization performed by far more sophisticated methods.