Observation and Control of exotic magnetic domain structures in ferromagnetic CeRu$_{2}$Ga$_{2}$B

The structure of magnetic domains in a single crystal of CeRu$_{2}$Ga$_{2}$B was investigated using low-temperature magnetic force microscopy (MFM) over a wide range of fields and temperatures. The low Curie temperature (T$_{C}\approx $16 K) allows for extensive tunability, revealing~a rich variety of magnetic states including branched stripes, bubble domains, and finger-like domains. In addition to~the higher~spatial resolution, the advantage of MFM over optical imaging techniques~is~the~ability~to~manipulate~magnetic domains. In particular, we are able to manipulate (move and destroy) individual circular domains~with~the MFM tip, which suggests that we observe unusual spherical `bubble' domains (as opposed to~cylindrical ones, with round terminations~at the surface). Our results~clarify the origins and illustrate the diversity of the domain structures in nearly ferromagnetic compounds.