Magnetization reversal in multilayers based in weak perpendicular magnetic anisotropy (wPMA) materials is controlled by the nucleation and propagation of 3D magnetic textures such as Bloch points, merons, vortices and antivortices. In these samples the basic domain structure is made of parallel stripes with alternating up/down magnetization in the central layer surrounded by in-plane magnetized closure domains at top/bottom surfaces. Magnetic transmission X-ray microscopy has allowed us to resolve the details of the magnetization reversal process at different sample depths in GdCo/NdCo/Permalloy trilayers measuring dichroic images at the different element absorption edges. Defects in the stripe pattern (bifurcations and end-points) are the preferred locations for the nucleation of merons (i.e. half skyrmions) at the first stages of in-plane magnetization reversal. This process is controlled by a set of well defined topological rules, related with the symmetry breaking between top/bottom surfaces by the sense of stray field circulation. Then, magnetization reversal in each layer proceeds by the propagation of magnetic vortices, antivortices and Bloch points guided by the parallel stripe pattern, creating various magnetization configurations such as the cycloidal domains in Permalloy shown in Figs. 1 and 2. Preliminary results of the characterization of these 3D textures across the sample thickness will also be presented using our recently developed tomographic method.

Resumen del póster presentado al 10th International Symposium on Metallic Multilayers (MML), celebrado en Madrid (España) del 17 al 21 de junio de 2019.

Work supported by Spanish MINECO (FIS2016-76058 (AEI/FEDER,EU)). AHR acknowledges a Marie Skłodowska-Curie grant (H2020-MSCA-IF-2016-746958).