Creation, transport and detection of imprinted magnetic solitons stabilized by spin-polarized current

Abstract

With the recent proposition of skyrmion utilization in racetrack memories at room temperature, skyrmionics has become a very attractive field. However, for the stability of skyrmions, it is essential to incorporate the Dzyaloshinskii-Moriya interaction (DMI) and the out-of-plane magnetic field into the system. In this work, we explore a system without these interactions. First, we propose a controlled way for the creation of magnetic skyrmions and skyrmioniums imprinted on a ferromagnetic nanotrack via a nanopatterned nanodisk with the magnetic vortex state. Then we investigate the detachment of the imprinted spin textures from the underneath of the nanodisk, as well as its transport by the spin-transfer torque imposed by spin-polarized current pulses applied in the nanotrack. A prominent feature of the moving imprinted spin texture is that its topological number Q is oscillating around the averaged value of Q = 0 as if it is a resonant state between the skyrmions with Q = ±1 and the bubble with Q = 0. We may call it a resonant magnetic soliton (RMS). A RMS moves along a straight line since it is free from the skyrmion Hall effect. In our studied device, the same electrodes are employed to realize the imprinted spin texture detachment and its transport. In addition, we have investigated the interaction between the RMS and a magnetic tunnel junction sensor, where the passing of the RMS in the nanotrack can be well detected. Our results would be useful for the development of novel spintronic devices based on moveable spin textures. a J = 10x10 8 A.cm -2 J = 55x10 8 A.cm -2 d b c Ku1=2x10 5 J/m 3 Ku1=3x10 5 J/m 3 Ku1=4x10 5 J/m 3 Ku1=5x10 5 J/m 3

Skyrmion-electronics: writing, deleting, reading and processing magnetic skyrmions toward spintronic applications

“…As the skyrmionium has a zero skyrmion number, it is immune from the SkHE and can be used to reliably delivery information in narrow and long nanotracks. Recently theoretical and simulation works have demonstrated that both spin currents and spin waves are able to drive skyrmioniums into motion in narrow nanotracks [174,229,230,232]. In 2018, Zhang et al [231] realized the real-space observation of a skyrmionium in ferromagnetic thin films coupled to a magnetic topological insulator [see Fig.…”

Skyrmionium – high velocity without the skyrmion Hall effect

“…Skyrmionium can be moved inside a nanotrack by spin waves 61 , 62 , magnetic field gradient 31 , 33 and spin-polarized current 32 , 34 , 63 . In this section, we demonstrate the spin current-dependent dynamics of a skyrmionium in comparison with a skyrmion and analyze the skyrmionium stability under the current action.…”

Robust dynamics of antiferromagnetic skyrmion driven by spin-polarized current in small thin disks

“…Recently, it was experimentally observed magnetic skyrmions in ferrimagnetic GdFeCo films [14] which have similar structures to antiferromagnets. It has been also claimed that a suitable spinpolarized current (SPC) could induce the appearance of AFM skyrmions [13] and that they could move for very long distances parallel to such a current [15][16][17], making them feasible information carriers for technological skyrmion-based devices. In this sense, it was shown that skyrmions lying in AFM thin disks are promising candidates to a new generation microwave signal generators [18].…”