Magnetic textures and singularities in ferri/ferromagnetic multilayers

The stacking of ferrimagnetic and ferromagnetic films leads to a competition between magnetic interactions that can stabilize Bloch points and other singularities at the interfaces. In this work, GdxCo1-x/NdCo5/GdyCo1-y trilayers, with different thicknesses, have been prepared. By tuning the stoichiometry of the Gd-Co outer layers, the Co magnetic sublattice dominates in one layer, whereas the opposite side is Gd dominated. In this way, in-depth magnetization domain walls can be created due to the balance between exchange and magnetostatic interactions. In addition, the weak perpendicular magnetic anisotropy of the Nd-Co central layer induces a stripe domain pattern, supporting the formation of Bloch points, meron-like textures, and vortex-antivortex pairs. The interaction between both types of structures, in-depth domain walls and magnetic singularities, has been studied by a combination of macroscopic Magneto-Optical Kerr Effect and Vibrating Sample Magnetometry measurements with microscopic Magnetic Force Microscopy and element selective magnetic Transmission soft X-ray Microscopy imaging. The results confirm marked changes in the magnetic properties of the trilayers, as compared with those single NdCo5 films, and the formation of complex magnetic textures, associated with partial magnetization reversal, where magnetic singularities are formed.This work was supported by Spanish MINECO under Project No. FIS2016-76058 (AEI/FEDER, UE), and Spanish MCI under Project No. PID2019-104604RB/AEI/10.13039/501100011033. These experiments were performed at the MISTRAL beamline at ALBA Synchrotron with the collaboration of ALBA staff. David Martínez Blanco, from Servicios Científico-Técnicos (Unidad de medidas magnéticas/RMN sólidos) Universidad de Oviedo, is acknowledged for VSM measurements. A. H.-R. acknowledges the support from European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant ref. H2020-MSCA-IF-2016-746958. J. H. acknowledges the support from Vicerrectorado de Investigación of Universidad de Oviedo (Plan de Apoyo y Promoción de la Investigación 2020).Peer reviewe