Role of SSW on thermal-gradient induced domain-wall dynamics

We study the thermal gradient (TG) induced domain wall (DW) dynamics in a uniaxial nanowire in the framework of the Stochastic-Landau-Lifshitz-Gilbert equation. TG drives the DW in a certain direction, and DW (linear and rotational) velocities increase with TG linearly, which can be explained by the magnonic angular momentum transfer to the DW. Interestingly, from Gilbert damping dependence of DW dynamics for fixed TG, we find that the DW velocity is significantly smaller even for lower damping, and DW velocity increases with damping (for a certain range of damping) and reaches a maximal value for critical damping which is contrary to our usual desire. This can be attributed to the formation of standing spin wave (SSW) modes (from the superposition of the spin waves and their reflection) together with travelling spin wave (TSW) modes. SSW does not carry any net energy/momentum to the DW, while TSW does. Damping alpha compels the spin current polarization to align with the local spin, which reduces the magnon propagation length and thus alpha hinders to generate SSWs, and contrarily the number of TSWs increases, which leads to the increment of DW speed with damping. For a similar reason, we observe that DW velocity increases with nanowire length and becomes saturated to maximal value for a certain length. Therefore, these findings may enhance the fundamental understanding as well as provide a way of utilizing the Joule heat in the spintronics (e.g. racetrack memory) devices.

Automated summary

The effect of thermal gradient on the dynamics of domain wall in a one-dimensional nanowire is studied. It is found that the thermal gradient can drive the domain wall motion, and the domain wall velocity increases linearly with the thermal gradient. Interestingly, it is observed that the domain wall velocity increases with damping in a certain range and reaches a maximum at critical damping.