Skyrmion and skyrmionium formation in the two-dimensional magnet Cr2Ge2Te6

The recently discovered 2D magnets represent versatile building blocks for spintronic devices. In particular, the out-of-plane 2D ferromagnets Fe3GeTe2 and Cr2Ge2Te6 (CGT) are attracting strong attention, owing to their ability to host topological spin textures. Among these, CGT is particularly interesting, as its semiconducting property could facilitate electric field control over the spin textures. Here, we systematically explore the magnetic phases of an exfoliated CGT flake with a thickness on the order of 50 nm by scanning transmission x-ray microscopy using three different measurement protocols. The domain periodicity was found to decrease with increasing temperature and decreasing flake thickness, the latter of which can be attributed to the relatively small magnetic anisotropy of CGT. Moreover, the magnetic phase diagram of CGT features a high-temperature skyrmion phase pocket, and skyrmionium formation occurs upon zero-field cooling. The sensitivity of the skyrmions to magnetic field changes indicates that dipolar interactions play a major role in stabilizing these magnetic spin textures.