Trajectory and frequency of vortex gyration in a multi-nanocontact geometry

Abstract

Nonlinear vortex gyrotropic motion in a three-nanocontacts system is investigated by micromagnetic simulations and analytical calculations. Three out-of-plane spin-polarized currents are injected into a nanodisk through a centered nanocontact and two off-centered nanocontacts, respectively. For current combination (i p1 , i p0 , i p2 ) = (−1, 1, −1), the trajectory of the vortex core is a peanut-like orbit, but it is an elliptical orbit for (i p1 , i p0 , i p2 ) = (1, 1, −1). Moreover, the gyrotropic frequency displays peaks for both current combinations. Analytical calculations based on the Thiele equation show that the changes of frequency can be ascribed mainly to the forces generated by the Oersted field accompanying the currents. We also demonstrate a dependence of eigenfrequency shifts on the direction and distance of the applied currents.

Magnetic vortex gyration mediated by point-contact position*

“…For the thin disk with L = 15 nm, the eigenfrequency first increases with j increasing and it turns a constant with j further increasing, and the thinner disk has similar dependence of eigenfrequency on the j as demonstrated in our previous study. [22] However, the eigenfrequency first increases and then decreases with j further increasing, which is a peculiar dynamical phenomenon in thicker disks. Figure 3(b) illustrates the dependence of eigenfrequency on current density j in nanodisks with the same thickness.…”

“…[20,21] Furthermore, our research found that the position and the size of point-contact can control the eigenfrequency of MV gyration. [15,22,23] Taking into account the previous studies and considering the better application of MV, [24] we particularly focus on the MV gyration in permalloy (Py) nanodisks with different sizes in this paper and investigate the effects of the point-contact position on MV gyration, including the critical current density of MV gyration, eigenfrequency, trajectory, velocity, and the time for a magnetic vortex to obtain the steady gyration.…”

Faster vortex core switching with lower current density using three-nanocontact spin-polarized currents in a confined structure

“…[33,34] We found that the trajectory and frequency of VC were also influenced by the current direction and distance. [35,36] These studies inspired us to design a new model to study the VC switching, where the out-of-plane spin-polarized currents are injected through a three-nanocontact geometry with tunable center-to-center distance and different current directions to make a nonuniform system, making it easier to excite the VC to switch with shorter time and less current density.…”