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Register a new userSpin wave driven domain wall motion in easy-plane ferromagnets
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In easy-plane ferromagnets, all magnetic dynamics are restricted in a specific plane, and the domain wall becomes massive instead of gyroscopic. Here we show that the interaction between domain wall and spin wave packet in easy-plane ferromagnets takes analogy to two massive particles colliding via attraction. Due to mutual attraction, the penetration of spin wave packet leads to backward displacement of the domain wall, and further the penetration of continuous spin wave leads to constant velocity of domain wall. The underlying temporary exchange of momentum, instead of permanent transfer of linear and angular momenta, provides a new paradigm in magnonically driving domain wall.
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We demonstrate optical manipulation of the position of a domain wall in a dilute magnetic semiconductor, GaMnAsP. Two main contributions are identified. Firstly, photocarrier spin exerts a spin transfer torque on the magnetization via the exchange interaction. The direction of the domain wall motion can be controlled using the helicity of the laser. Secondly, the domain wall is attracted to the hot-spot generated by the focused laser. Unlike magnetic field driven domain wall depinning, these mechanisms directly drive domain wall motion, providing an optical tweezer like ability to position and locally probe domain walls.
Domain-wall (DW) motion in magnetic nanostrips is intensively studied, in particular because of the possible applications in data storage. In this work, we will investigate a novel method of DW motion using magnetic field pulses, with the precession torque as the driving mechanism. We use a one dimensional (1D) model to show that it is possible to drive DWs in out-of-plane materials using the precession torque, and we identify the key parameters that influence this motion. Because the DW moves back to its initial position at the end of the field pulse, thereby severely complicating direct detection of the DW motion, depinning experiments are used to indirectly observe the effect of the precession torque. The 1D model is extended to include an energy landscape in order to predict the influence of the precession torque in the depinning experiments. Although preliminary experiments did not yet show an effect of the precession torque, our calculations indicate that depinning experiments can be used to demonstrate this novel method of DW motion in out-of-plane materials, which even allows for coherent motion of multiple domains when the Dzyaloshinskii-Moriya interaction is taken into account.
We investigate ferrimagnetic domain wall dynamics induced by circularly polarized spin waves theoretically and numerically. We find that the direction of domain wall motion depends on both the circular polarization of spin waves and the sign of net spin density of ferrimagnet. Below the angular momentum compensation point, left- (right-) circularly polarized spin waves push a domain wall towards (away from) the spin-wave source. Above the angular momentum compensation point, on the other hand, the direction of domain wall motion is reversed. This bidirectional motion originates from the fact that the sign of spin-wave-induced magnonic torque depends on the circular polarization and the subsequent response of the domain wall to the magnonic torque is governed by the net spin density. Our finding provides a way to utilize a spin wave as a versatile driving force for bidirectional domain wall motion.
We report on current induced domain wall propagation in a patterned GaMnAs microwire with perpendicular magnetization. An unexpected slowing down of the propagation velocity has been found when the moving domain wall extends over only half of the width of the wire. This slowing down is related to the elongation of a longitudinal wall along the axis of the wire. By using an energy balance argument, the expected theoretical dependence of the velocity change has been calculated and compared with the experimental results. According to this, the energy associated to the longitudinal domain wall should change when a current passes through the wire. These results provide possible evidence of transverse spin diffusion along a longitudinal domain wall.
Polarization, denoting the precession direction with respect to the background magnetization, is an intrinsic degree of freedom of spin wave. Using magnetic textures to control the spin wave polarization is fundamental and indispensable toward reprogrammable polarization-based magnonics. Here, we show that due to the intrinsic cubic anisotropy, a $90^circ$ antiferromagnetic domain wall naturally acts as a spin wave retarder (wave-plate). Moreover, for a $90^circ$ domain wall pair developed by introducing a second domain in a homogenous antiferromagnetic wire, the sign of retarding effect can be flipped by simply switching the direction of the intermediate domain. The intimate connection between rich states of magnetic domains and the spin wave polarization in cubic anisotropic systems, offers new possibilities in constructing purely magnetic logic devices.
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