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Magnetic skyrmions, which are topological spin configuration, have gained interest in the past few years. However, skyrmions suffer from the skyrmion Hall effect, a phenomenon where skyrmions deflect from the path of the electron flow and annihilate at the edge of the track. There are attempts to overcome this effect using synthetic antiferromagnetic layer structures and ferrimagnetic layer structures. Herein, a new approach based on introducing Dzyaloshinskii–Moriya interaction (DMI) energy wells is reported to direct the motion of skyrmions in a nanowire. It is shown through simulations that by creating DMI energy wells with a critical DMI value, a skyrmion moves within the boundaries set by the energy wells. It is also shown that the diameter of a skyrmion can be reduced by decreasing the space between the DMI energy wells. The proposed DMI energy well enables packing of skyrmion tracks at a high density. In this view, the effect of magnetostatic interactions between multiple skyrmions on their motion in parallel tracks is also investigated. Furthermore, the effect of changing the distance between skyrmions on magnetostatic interactions is studied. These results offer a new path toward maneuvering the skyrmion motion for racetrack memory or logic devices.

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domains store information states and the information is read by moving the domains. [11,[14][15][16][17][18] Domain wall movement can also be explored for energy harvesting by converting stress into changes in magnetization and thus into electrical voltage. In the energy harvesting investigations reported so far, domain wall motion is accomplished only in multiferroic structures, where stress was induced by providing an electrical energy to the ferroelectric layers. [19][20][21][22][23][24][25] Employing significant amounts of electrical energy, however, defeats the purpose of energy harvesting. Moreover, ceramic ferroelectric layers, like PZT, require high-temperature deposition or postdeposition annealing (>400 °C) under severe oxidation conditions, which inevitably degrade the magnetic properties. [26] Therefore, stress-induced motion of domain walls in pure magnetic films without the use of ferroelectric layers and a supplied energy is a better approach for self-power generation. In the past, amorphous magnetic materials have been studied for domain wall dynamics under stress. [27,28] Pickup of voltage using a pickup coil was used for sensing the domain wall motion. [29][30][31] An analytical model for stress-induced transverse domain wall movement in ferromagnetic nanostripe has also been proposed. [32] In this article, we report that the domain walls in magnetic microwires made of crystalline ferromagnetic films can be moved by merely applying mechanical stress. The key recipes for the successful observation of such domain wall movement are: (i) a magnetic stack of CoNi/Fe 65 Co 35 /CoNi with which we have controlled the microstructures, (ii) an induced magnetic easy axis that we set by the direction of fringing magnetic field during the deposition (see the Supporting Information), and (iii) the use of flexible substrates with which we could enhance the stress delivered to the device from ambient sources, which is otherwise impossible with rigid substrates like Si. With a prototype device, we have shown in this article, the motion of domain walls under applied stress and have harvested energy.

Microwave generation has been extensively investigated due to their application in telecommunication and promising use in emerging technologies like internet‐of‐things (IoT) devices. The current approaches to generate microwave using voltage‐controlled oscillators have the problem of high power consumption. Spin torque oscillators have been investigated as an alternative, but they suffer from a weak output signal. Hence, there is a need for an alternative approach which overcomes these issues. Here a new approach is reported, which relies on the motion of domain walls to generate microwave with strong signal and lower power consumption. In this study, a magnetic nanowire with a sequence of oppositely magnetized domains in one half of the nanowire is simulated. The domain walls are moved by applying spin–orbit torque to the nanowire. It is proposed to generate microwave by detecting the changes in magnetization value using a magnetic tunnel junction in real application. The oscillating frequency of magnetization is found to be in GHz. It is demonstrated that the frequency can be tuned by varying the applied current density. The outcome of this work promises the application of the reported method to generate microwave in nanoscale devices of the future.