Topology and origin of effective spin meron pairs in ferromagnetic multilayer elements
Sebastian Wintz, Christopher Bunce, Andreas Neudert, Michael Körner, Thomas Strache, Matthias Buhl, Artur Erbe, Sibylle Gemming, Jörg Raabe, Christoph Quitmann, and Jürgen Fassbender
Accepted
We report on pairs of converging-diverging spin vortices in Co/Rh/NiFe trilayer disks. The lateral magnetization distribution of these effective spin merons is directly imaged by means of element-selective x-ray microscopy. By this method, both the divergence and circulation states of the individual layers are identified to be antisymmetric. Reversal measurements on corresponding continuous films reveal that biquadratic interlayer exchange coupling is the cause for the effective meron pair formation. Moreover their three-dimensional magnetization structure is determined by micromagnetic simulations. Interestingly, the magnetic induction aligns along a flux-closing torus. This toroidal topology enforces a symmetry break, which links the core polarities to the divergence configuration.