Micromagnetic Study of Spin-Transfer-Driven Vortex Dipole and Vortex Quadrupole Dynamics

Magnetic vortex and antivortex are nonuniform magnetization configurations that can be also achieved in spin-torque oscillators either isolated or as vortex-antivortex pair, namely vortex dipole. This paper shows a systematic micromagnetic study about the identification of soliton dynamics characterized by different skyrmion numbers. Our results show the excitation of both rotation and translation of vortex dipoles and rotating vortex quadrupoles. Those different scenarios can be achieved by changing the geometrical parameters of spin valve and the amplitude of external field. The origin of the different dynamical behaviors is explained within a micromagnetic framework.