Abstract
Magnetic skyrmions are promising candidates as information carriers for the next-generation spintronic devices because of their small size, facile current-driven motion and topological stability. The controllable nucleation and motion of skyrmions in magnetic nanostructures will be essential in future skyrmionic devices. Here, we present the microwave assisted nucleation and motion of skyrmion-chains in magnetic nanotrack by micromagnetic simulation. A skyrmion-chain is a one-dimensional cluster of equally spaced skyrmions. A skyrmion-chain conveys an integer bit n when it consists of n skyrmions. A series of skyrmion-chains with various lengths is generated and moved in the nanotrack driven by spin-polarized current. The period, length and spacing of the skyrmion-chains can be dynamically manipulated by controlling either the frequency of the microwave field or the time dependent spin-polarized current density. A skyrmion-chain behaves as a massless particle, where it stops without delay when the current is stopped. Their velocity is found to be linearly dependent on the current density and insensitive to the frequency and amplitude of the excitation microwave field. Uniform motion of trains of skyrmion-chains in nanotrack offers a promising approach for spintronic multi-bit memories containing series of skyrmion-chains to represent data stream.
Highlights
Approximately 3 nm to 100 nm depending on material parameters
Most of the reported observations are on the skyrmion lattices in thin films, from the application point of view, skyrmionic devices will require either individual or multiple skyrmions to be efficiently manipulated in magnetic nanostructures
The device consists of Co/Pt nanotrack with a narrow end on the left side, an antenna for generating microwave magnetic field to write domain walls (DWs) pairs, and the spin-polarized electron current for shifting DW pairs and skyrmion-chains along the x-direction
Summary
Approximately 3 nm to 100 nm depending on material parameters. These novel spin textures are topologically protected and their topological stability drastically reduces the influence of defects so as to avoid a continuous deformation of the field configuration[23]. It was recently demonstrated experimentally that a spin-polarized current with small current density (~ 106 A/m2) can drive the motion of the skyrmion lattices[32,33], which is about 5 orders of magnitude smaller than that required to shift DWs (~1011 A/m2)[2]. This has been attributed to their efficient coupling to the current via spin-transfer torque by a spin-Magnus force mechanism[31,32,34,35]. It is desirable to achieve a train of skyrmion-chains with their properties can be manipulated for potential spintronic applications
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