Spin-orbit torque nucleation and annihilation of magnetic droplet solitons

Magnetic droplet solitons can form in thin films with perpendicular magnetic anisotropy (PMA) and zero damping. They have mostly been realized using nano-contact geometries to locally counteract the intrinsic damping using spin-transfer torques. A more efficient pathway for current controlled magnetization dynamics is given by spin-orbit torques (SOTs). Due to symmetry restrictions these torques can conventionally only manipulate in-plane magnetizations efficiently. However, mirror symmetry breaking in non-colinear antiferromagnets due to magnetic order can generate unconventional out-of-plane SOTs that can be used to manipulate magnetizations in PMA films. Here, we investigate the nucleation and annihilation behavior of droplets from unconventional spin-orbit torques in rectangular films using micromagnetic simulations. We find that the current pulse amplitude and duration affect the number of droplets nucleated and the nucleation time. By precisely controlling the current pulse we can add and subtract droplets from our system on demand. Additionally, an external magnetic field affects the droplet size and position.