Stabilization and switching of magnetic merons in AuPt/Co/W(110) epitaxial thin films

Abstract

Topological magnetic textures such as skyrmions have been extensively studied during the last decade due to their potential application in spintronics devices. In ultrathin films systems, a key parameter to stabilize chiral topological magnetic textures is the Dzyaloshinskii-Moriya interaction (DMI), obtained at the interfaces between ferromagnetic layers and heavy-metals, promoting a unique chirality of the magnetic texture. We focus on an ultrathin epitaxial Au1-xPtx/Co(0.6-0.8nm)/W(110) trilayer, a model system exhibiting perpendicular magnetic anisotropy (PMA) and interface DMI. The epitaxial growth of Co (0001) on W(110) gives rise to a C2v crystal symmetry at the Co/W(110) interface. This symmetry results into a biaxial magnetic anisotropy, with an in-plane easy axis along the W[1-10] direction, and into an anisotropic DMI [1].In this work, we have used Brillouin light spectroscopy to show the effect of the Pt-to-Au composition on the PMA and DMI of the trilayer. The balance between the different magnetic interactions, give rise to the stabilization in circular nanodots of different magnetic textures such as elliptical skyrmions [2] or magnetic merons [3], which have been observed with X-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM). In this presentation, we will focus on the stabilization of magnetic merons which are radial chiral textures with a topological charge Q=1/2 and topologically equivalent to a circular vortex. We will discuss the stabilization of magnetic merons, and how the topological charge can be switched under the application of an external perpendicular magnetic field as shown with XMCD-PEEM (Figure 1) **