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.The magnetic domain wall motion induced by spin-transfer torque (STT) from a spin-polarized electrical current has attracted growing interest because of its fundamental relevance and potential applications in spintronic devices such as Racetrack memory and logic devices. 1-3 It is widely recognized that there are two types of STT acting on the wall when a spin-polarized current flows through it, namely the adiabatic STT and nonadiabatic STT. 4,5 The adiabatic STT comes from the adiabatic reversal of conduction electron spins, which induces a reaction torque on the wall as required by the conservation of angular momentum. 6 However, the origin of nonadiabatic STT still remains controversial. There are many contributions to this torque, such as spin-orbit interactions, spin-flip scattering, etc. 7-9 When the domain wall is narrow, the momentum transfer due to the electron reflection by the wall also contributes to the nonadiabatic STT. 10 The influence of the adiabatic and nonadiabatic STT on the wall motion is different. The adiabatic STT plays a more important role at the initial motion of the wall. It provides an initial velocity and causes the wall to move, but finally, it is balanced by an internal restoring torque and the wall motion ceases. 6 In contrast, the nonadiabatic STT behaves like a magnetic field and can sustain a steady-state wall motion. 5 Recently, the noncharge-based spin current, magnonic spin current, is proposed 11 and experimentally demonstrated. 12 Similar to the spin-polarized electrical current, the magnonic spin current also leads to the STT in the magnet and can be exploited to control the spin structures, including the displacement of the domain wall. Hinzke et al. 13 first demonstrated theoretically that a single domain wall in a nanowire can be displaced by a magnonic spin current due to the temperature gradient. Yan et al. 14 showed that a spin wave excited by a microwave field can also drive a wall motion. They suggested that the mechanism of wall motion is the spin transfer torque resulting from the angular momentum transfer between the magnons and the local magnetization in the wall. As a magnon moves across the wall, its angular moment is changed by 2h which is absorbed by the wall, making the wall propagate in the opposite direction to that of the magnon. It is wo...

Spin-wave propagation and spin-wave induced domain wall motion in nanostrips with a Néel wall are studied by micromagnetic simulations. It is found that the reflection of spin waves by the wall can be resonantly excited due to the interaction between spin waves and domain-wall normal modes. With the decrease of the saturation magnetization Ms (and the consequent increase of the wall width), the reflection is diminished and complete transmission can occur. The domain wall motion induced by spin waves is closely related to the spin-wave reflectivity of the wall, and may exhibit different types of behavior. The reflected spin waves (or magnons) give rise to a magnonic linear momentum-transfer torque, which drives the wall to move along the spin wave propagation direction. The maximal velocity of the domain wall motion corresponds to the resonance reflection of the spin waves. The transmitted spin waves (or magnons) lead to a magnonic spin-transfer torque, which drags the wall to move backwardly. The complicated domain wall motion can be described qualitatively by a one-dimensional model incorporating both the magnonic linear momentum-transfer torque and the magnonic spin-transfer torque. The results obtained here may find use in designing magnonic nanodevices.

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