A Co disk on a Pt underlayer is initialised with a number of skyrmions. Using two Au contacts to the Co disk, an electrical current is applied. The 3D spin transport solver is used to obtain the spin torques acting on the skyrmions, both spin-transfer torques in the Co disk, and interfacial spin-orbit torques at the Co/Pt interface. The skyrmion movement direction is reversed when the current polarity changes. Since the charge and spin transport solver is self-consistent, the simulation accounts for non-uniformity of charge and spin current densities, including diffusive spin torques due to inter-layer spin diffusion (see S. Lepadatu, Scientific Reports 9, 9592 (2019))
Below, the charge current density is shown in the Au contacts, the magnetisation configuration in the Co disk, and the spin accumulation in the Pt layer:
Another example, this time with 4 electrical contacts: the contact on the left is the ground, and the other 3 contacts are at the same potential. The duration of the simulation is 10 ns. The Co disk diameter is 640 nm.