Circularly polarized X-ray Resonant Magnetic Scattering in a 2D chess array of square nanomagnets: vortex asymmetries and chirality

Abstract

Circularly polarized X-ray Resonant Magnetic Scattering (CXMRS) has been used to study the magnetic states of a 2D array of Py square nanomagnets of 700 nm lateral size arranged in a chess lattice of 1000 nm lattice parameter. Magnetization reversal of each Py nanosquare occurs by the nucleation of magnetic vortices as indicated by VSM hysteresis loops and confirmed by XMCD PEEM images taken at remanence. Magnetic scattering images have been recorded using circular polarized light at different applied fields (Fig.1). At low fields, the magnetic diffraction pattern of the square array of nanomagnets becomes asymmetric in intensity in the direction transversal to the incident plane. The asymmetry is inverted when the direction of the applied magnetic field is inverted. The field evolution of magnetic diffraction patterns is analysed in terms of the displacements of vortex cores from each square center during the magnetization reversal process. The observed asymmetries require a breaking of the degeneracy of vortex states with CW and CCW chirality, as sketched in Fig.2, creating an effective fanning configuration across the array.