Current-Driven Vortex-Antivortex Pair Rotation in a Magnetic Thin Film with Multiple Contacts

We theoretically analyzed the current-driven vortex-antivortex pair rotation in a magnetic thin film where spatially localized spin-polarized current is injected through two nonmagnetic nanocontacts. We performed the micromagnetic simulations and found that the dynamics of magnetization strongly depends on the distance between the contacts. If the distance between the contacts is large enough to separate the trajectories of vortex-antivortex (VA) pair rotation, the two VA pairs rotate around each contact with an angular frequency identical to that of a single contact system. In contrast, if the distance between the contacts is so short that the trajectory of each VA pair rotation can overlap with each other, two VA pair rotations are merged into one VA pair rotation whose trajectory encloses the two contacts as if a large elliptical contact exists at their midpoint. We showed that the rotation frequency decreases with increasing length of the trajectory. The rotation frequency for the trajectory enclosing the two contacts is much smaller than that for the single contact system. We also found that there is an intermediate distance where VA pair rotation collapses.