Abstract
Magnetic skyrmion transport has been primarily based on the use of spin torques which require high current densities and face performance deterioration associated with Joule heating. In this work, we derive an analytical model for energy efficient skyrmion propagation in an antiferromagnetically-coupled bilayer structure using a magnetic anisotropy gradient. The interlayer skyrmion coupling provides a strong restoring force between the skyrmions, which not only prevents annihilation but also increases their forward velocity up to the order of km s–1. For materials with low Gilbert damping parameter, the interlayer skyrmion coupling force can be amplified up to ten times, with a corresponding increase in velocity. Furthermore, the analytical model also provides insights into the dynamics of skyrmion pinning and relaxation of asymmetric skyrmion pairs in bilayer-coupled skyrmion systems.
Highlights
Magnetic skyrmions are particle-like chiral magnetization states that are promising as an information carrier due to their attractive characteristics such as nanometre dimensions, and topological stability [1,2,3,4,5,6,7,8,9,10,11]
In the implementation of a magnetic skyrmion racetrack memory, the transport techniques explored far have been mainly limited to the use of spin-polarized electrical current injection which utilizes spin transfer torque (STT) and spin–orbit torque (SOT)
Skyrmion velocity dependence on magnetic anisotropy strength and gradient We investigated the dependence of the skyrmion speed on both the steepness of the Ku gradient and the value of Ku at the centre of the skyrmion
Summary
Magnetic skyrmions are particle-like chiral magnetization states that are promising as an information carrier due to their attractive characteristics such as nanometre dimensions, and topological stability [1,2,3,4,5,6,7,8,9,10,11]. A wide range of alternative propagation techniques has been proposed to overcome the issue of Joule heating and for applications in insulating skyrmions. These alternatives include magnetic field gradients [17,18,19], electric field gradients [20], temperature gradients [21,22,23], spin waves and magnons [24,25,26]. These systems face various challenges in their implementation and scalability, while spin waves face attenuation and scattering about each skyrmion along a long nanowire
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