Controllable nucleation and propagation of topological magnetic solitons in CoFeB/Ru ferrimagnetic superlattices

We control the nucleation and propagation of topological magnetic solitons in synthetic ferrimagnetic (CoFeB/Ru)N superlattices (N $=$ 6). This is achieved by carefully tuning the anisotropy and thickness of one of the edge layers, making it different from the other layers of the superlattice. Sharp solitons can be nucleated at one edge of the system, then unidirectionally propagated using external magnetic fields. Experimental results are modeled with macrospin simulations. We present a numerical phase diagram which maps the general behavior for the nucleation and propagation of solitons in ferrimagnets.