  Merons are nontrivial topological spin textures highly relevant for many
phenomena in solid state physics. Despite their importance, direct observation
of such vortex quasiparticles is scarce and has been limited to a few complex
materials. Here we show the emergence of merons and antimerons in recently
discovered two-dimensional (2D) CrCl3 at zero magnetic field. We show their
entire evolution from pair creation, their diffusion over metastable domain
walls, and collision leading to large magnetic monodomains. Both quasiparticles
are stabilized spontaneously during cooling at regions where in-plane magnetic
frustration takes place. Their dynamics is determined by the interplay between
the strong in-plane dipolar interactions and the weak out-of-plane magnetic
anisotropy stabilising a vortex core within a radius of 8-10 nm. Our results
push the boundary to what is currently known about non-trivial spin structures
in 2D magnets and open exciting opportunities to control magnetic domains via
topological quasiparticles.
