Multilayer racetrack design based on synthetic ferrimagnetic skyrmions

Magnetic skyrmions have emerged as promising candidates for next-generation spintronic devices due to their nanoscale size, high stability, and low power consumption. However, their practical application still faces several technical challenges. In the two-lane racetrack device, binary signals “0” and “1” are represented by the lane occupied by a ferromagnetic skyrmion, providing higher recognition accuracy compared to conventional single-track devices, which rely on the presence or absence of a skyrmion. However, the strong skyrmion Hall effect (SHE) can lead to tunneling between the lanes under low barrier conditions, which may cause signal disorder. Increasing the barrier can suppress tunneling, but it will weaken interactions between skyrmions and make the device more susceptible to material defects. To overcome these limitations, we propose a multilayer racetrack device model based on synthetic ferrimagnetic (SFIM) skyrmions. By utilizing the tunable and weak SHE of SFIM skyrmions, the proposed model is able to prevent skyrmion tunneling while preserving signal correlation, thereby further enhancing signal stability. The feasibility of the model is validated through micromagnetic simulations using MuMax3 and analytical analysis based on the Thiele equation. Notably, compared to the two-lane racetrack model, our model achieves nearly an order-of-magnitude increase in the threshold current under the same magnetic anisotropy barriers. This significantly broadens the driving current range within which the device can operate stably, thereby enhancing its overall performance.