The interactions between spin wave and stacked domain walls.

In this study, the interactions between spin wave (SW) and stacked domain walls in a magnetic nanostrip are investigated via micromagnetic simulation. It is found that under the excitation of SW, the metastable TWVW structure consisting of a transverse wall (TW) and a vortex wall (VW) may transform into a 360° wall or may completely annihilate depending on the frequency and amplitude of the SW. In contrast, stacked TWs (STWs) structure shows good robustness. Similar to a single TW, the STWs can be moved by SW and the inside TWs exhibit coherent motions. Notably, the frequency dependence of STWs' velocity demonstrates obvious emergence, shift and disappearance of the resonant peaks. Such changes are found to be in accordance with SW reflection, which thus agrees with the mechanism of linear momentum transfer torque (LMTT). In concern with the SW transmission through STWs, we show that by varying TWs number and SW frequency, a wide range of transmission efficiency η can be obtained. At certain frequencies, η may increase with TWs number and may go beyond 100%, which indicates a lowered attenuation by STWs. On the other hand, the phase shift of the transmitted SW always increases linearly with the TWs number and can be resonantly enhanced at frequencies same as that of TWs normal modes. Mapping of SW reveals that the phase shift is a result of fast propagation of SW through TWs. The fast propagation and the low attenuation of SW through STWs suggests that STWs may serve as an excellent SW channel. Meanwhile, the induced STWs motion and the controlled SW transmission and phase shift by STWs also promises great uses of STWs in future magnonic devices and domain wall devices.

The origin of spin wave pulse-induced domain wall inertia.

The fundamental problem of domain wall (DW) inertia-the property that gives to inertial behaviors remains unclear in the physics of magnetic solitons. To understand its nature as well as to achieve accurate DW positioning and efficient manipulation of domain wall motion (DWM), spin wave (SW) pulse-induced DW transient effect is studied both numerically and theoretically in a magnetic nanostrip. It is shown for the first time that there occurs inevitable deceleration/automotion after SW pulse, which indicates nonzero DW inertia. The induced DWM is revealed to relate to two factors: energy storing within DW and out-of-plane tilting of DW. To explain the DWM dynamics, a one-dimensional collective model is developed to account for the excitation of spin wave pulse. The model successfully bridges DW energy, DW tilting and DW displacement and provides descriptions in accordance with numerical findings. It is made clear that the DW automotion hence DW inertia originate from the process of DW relaxation toward equilibrium. The DW inertia is expressed in terms of effective mass and turns out to be a time-dependent function with damping constant α as the governing parameter, which opposes the nature of intrinsic mass. For case containing multiple DWs, the total effective mass is shown to concern the reached velocity and stored energy of DWs instead of the number of DWs, which is against common intuition.