Switching between different vortex states in two-dimensional easy-plane magnets due to an ac magnetic field

Abstract

Using a discrete model of 2-dimensional easy-plane classical ferromagnets, we propose that a rotating magnetic field in the easy plane can switch a vortex from one polarization to the opposite one if the amplitude exceeds a threshold value, but the backward process does not occur. Such switches are indeed observed in computer simulations.

Equilibrium magnetisation structures in ferromagnetic nanorings

“…Our model of the IMV can be applied for the description of dynamical effects of the switching of the vortex polarisation [18,19,20]. We expect that the dynamical switching effects should be more pronounced in the ring geometry, because the vortex amplitude µ can smoothly vary and even change its sign.…”

Controlled vortex core switching in a magnetic nanodisk by a rotating field

“…5). The switching diagram differs from the one in Heisenberg magnets, where the vortex flipping is characterized mainly by a threshold curve B cr (ω) [7,10].…”

“…Note that this switching field should be strong enough, B s ∼ 2.5 kOe [16,17,18,19]. Another possibility to switch the vortex is to use a weak but fast rotating field B(t) [7,8,9,10]. The physical idea is very simple.…”

“…3. Mainly two magnon modes are excited in this system: symmetrical and azimuthal ones [7,10]. The azimuthal mode is caused by the influence of the in-plane field and the symmetrical one by the effective out-of plane field B ⊥ .…”

“…However, the rigid approach fails when considering the vortex dynamics under the influence of a strong or fast external force. In particular, it is known that external pumping excites internal modes in vortex dynamics in Heisenberg magnets, whose role is important for understanding the switching phenomena [6,7,8,9,10,11], and the limit cycles in the vortex dynamics [12,13].…”