Domain wall motion induced by the magnonic spin current

The spin-wave induced domain wall motion in a nanostrip with perpendicular magnetic anisotropy is studied. It is found that the domain wall can move either in the same direction or in the opposite direction to that of spin-wave propagation depending on whether the spin wave is reflected by the wall or transmitted through the wall. A magnonic momentum transfer mechanism is proposed and, together with the magnonic spin-transfer torque, a one-dimensional phenomenal model is constructed. The wall motion calculated based on this model is in qualitative agreement with micromagnetic simulations, showing that the model can describe the characteristics of spin-wave-induced wall motion and, especially, the wall motion direction.

Figure 1

Illustration of the Model PMA nanostrip with the geometry and dimensions. A 180° Bloch domain wall is positioned at the center $X=0$. The magnetization direction is represented by arrows. The gray area with $H$($t$) represents the region where spin waves are excited. The Cartesian coordinate system is shown on the higher left. The lower right inset shows the magnetization components of the wall profiles.

Figure 2

The wall displacement $X$ as a function of time $t$, induced by propagating spin waves of frequency (a) 22 GHz and (b) 70 GHz. The black squares are the micromagnetic simulation results. The red solid line and green dashed line represent the model calculation with α $=$ 0.01 and 0, respectively. The blue circle is the simulation results of wall motion driven by the equivalent spin-polarized electrical current.

Figure 3

(a) Simulated (black squares) and model calculated (red circles) wall velocity $v$ and (b) initial wall velocity $v_i$ as a function of the frequency. The amplified scale of the wall velocity induced by the spin wave with frequencies larger than 55 GHz is shown as an inset of (a). All the velocities are normalized by (ρ/$M_s$)${}^2$. The dashed lines are guides for the eye.

Figure 4

Transmission coefficient $T$ of spin wave passing through the domain wall (black solid line) and amplitude of spin wave ρ (red/dark gray solid line) as a function of the frequency.