Magnetic skyrmions are topologically protected nanoscale objects, which are promising building blocks for novel magnetic and spintronic devices. Here, we investigate the dynamics of a skyrmion driven by a spin wave in a magnetic nanowire. It is found that (i) the skyrmion is first accelerated and then decelerated exponentially; (ii) it can turn L-corners with both right and left turns; and (iii) it always turns left (right) when the skyrmion number is positive (negative) in the T- and Y-junctions. Our results will be the basis of skyrmionic devices driven by a spin wave.

The authors report on the switching of a magnetic vortex core in a submicron Permalloy disk, induced by a short current pulse applied in the film plane. Micromagnetic simulations including the adiabatic and nonadiabatic spin-torque terms are used to investigate the current-driven magnetization dynamics. They predict that a core reversal can be triggered by current bursts a tenth of a nanosecond long. The vortex core reversal process is found to be the same as when an external field pulse is applied. The control of a vortex core’s orientation using current pulses introduces the technologically relevant possibility to address individual nanomagnets within dense arrays.

Current-induced magnetization switching (CIMS) in low-resistance magnetic tunnel junctions was shown at average critical current densities ${\mathrm{(J}}_c{\text{=1.33×10}}^6\hspace{0.17em}{\mathrm{A/cm}}^2\mathrm{).}$ When large vertical currents pass through the junctions, spin-transfer torque, and vortex fields can rotate the magnetization of the free layer from the initial parallel state to a vortex state, resulting in 10.8% CIMS resistance change at zero-bias current, which is about half of the resistance change (22%) induced when switching is created by an external field. A micromagnetic simulation including the spin-transfer torque and the vortex field correctly predicts the critical negative-current-inducing switching from the parallel state into the vortex state, but fails to explain the reverse switching from the vortex state into the parallel state at an approximately symmetric positive critical current. Lead fields were analyzed and found to be not the cause of the observed switching. The very small dependence of the switching currents on an external magnetic field suggests the existence of hot-spots where local current densities may be much larger.

Spin-torque-driven vortex dynamics are studied by micromagnetic modeling in a spin-valve pillar which contains a perpendicular polarizer and a vortex free layer. Two kinds of transient oscillations mediated by the vortex-core motion are observed. The oscillations are treated as the competition among the spin torque, gyroforce, Gilbert damping, and the restoring force, governed by the generalized Thiele equation [A. A. Thiele, J. Appl. Phys. 45, 377 (1974)]. The fundamental frequency is dominated by the gyrotropic motion, while the high-frequency oscillation is triggered by the balance of the spin torque and demagnetizing field. The polarity of the vortex core can be switched through a vortex-antivortex pair creation and annihilation process.