Rare Earth (RE)-Transition Metal (TM) alloys and bilayers in which there is a large antiferromagnetic (AF) coupling between the RE and TM have recently attracted large attention due to their potential interest for very fast domain wall (DW) motion, opening new possibilities for applications. We investigated the magnetic singularities (walls, Bloch points, merons…) occurring at the interfaces in ferri/ferrro/ferri magnetic trilayers based on GdxCo1-x/NdCo/GdyCo1-y combinations. By appropriate tuning of the composition, the upper GdCo layer will couple AF with the central NdCo layer (that has weak perpendicular anisotropy) whereas the bottom GdCo will exhibit ferromagnetic coupling as schematically depicted in panel a of Fig. 1. Micromagnetic simulations reveal that the singularities tend to localize at the interfaces with domain walls across the thickness (see Fig. 1(b)). Magnetic transmission X-ray microscopy (MTXM) at the Mistral beamline of the ALBA synchrotron allowed to characterize these complex magnetic structures: different shades of grey in the dichroic contrast indicate the presence of circulating domains across the thickness and enhanced contrast at the boundaries between domains suggest the presence of localized magnetic singularities (see Fig. 1(c)). Moreover, we performed a vector tomography using our method described in to obtain the full 3D magnetic configuration. We will discuss the different kinds of magnetic singularities observed in the sample and their topology

This work was supported by Spanish MICINN under Projects FIS2016-76058 and PID2019-104604RB (AEI/FEDER, UE), A.H.-R. acknowledges the support from European Union’s Horizon under Marie Skłodowska-Curie grant ref. H2020-MSCA-IF-2016-746958.

Trabajo presentado al Biennial Meeting of the Condensed Matter Divisions of the Spanish Royal Physics Society (CMD-GEFES), celebrado online del 31 de agosto al 4 de septiembre de 2020.

Peer reviewed