Direct imaging of chiral domain walls due to the Dzyaloshinskii-Moriya interaction in ferrimagnetic alloys at different temperatures

Abstract

Magnetic skyrmions are topological spin textures that can be stabilized by the Dzyaloshinskii-Moriya interaction [1,2]. There are particularly suitable for next generation spintronics devices, like the skyrmion-based racetrack memory [3]. Recent studies confirmed their current-driven skyrmion dynamics in ultrathin ferromagnets via spin-orbit torques [4], where the chirality and spin texture of the skyrmions are key. However, the topological Magnus effect leads to a transverse motion of ferromagnetic skyrmions due to their non-zero topological charge [5], which is disadvantageous for devices. Antiferromagnetically exchange-coupled skyrmions or compensated ferrimagnets could suppress this effect owing to an overall zero topological charge [6]. Especially at the angular momentum compensation temperature skyrmion propagation is predicted to be collinear with the current [7]. Here we explore a GdFeCo-based ferrimagnet system with perpendicular magnetic anisotropy. We demonstrate that in this system chiral worm domains as well as magnetic skyrmions can be observed using scanning electron microscopy with polarization analysis (SEMPA) (Figure 1). The high spatial resolution magnetic imaging technique reveals the domain wall spin structure as a function of temperature, with the observed structures found to be pure Néel-type spin textures, which is promising for devices. From the images we extract the domain wall width, which allows us to calculate the exchange stiffness for the system across the full temperature range.