Skyrmion Motion in Ferrimagnets Driven by Magnetic Anisotropy Gradient

The topological skyrmions in ferrimagnet systems provide new opportunities to investigate the fundamental spin dynamics. Effective manipulation of ferrimagnet skyrmion motion is a vital task for future spintronics applications, motivating intense research on magnetization dynamics with voltage as driving sources. In this work, the skyrmion in ferrimagnets driven by voltage controlled magnetic anisotropy gradients, which tends to move toward the low anisotropy area and has a constant velocity, is investigated. Thiele's theory analysis is reported on the velocities of the skyrmion dependencies on the anisotropy gradient, the net angular momentum density, and the damping coefficient, which are confirmed nicely by the atomistic simulations. It is demonstrated that the velocity of the skyrmion reaches to a maximum value at a nonzero net angular momentum density delta s different from the domain wall, and the Hall angle of ferrimagnet skyrmions can be controlled by delta s. The results are useful for the understanding of ferrimagnet skyrmion dynamics and may open an alternative way for the design of ferrimagnet spintronic devices. In ferrimagnets, the maximal velocity of skyrmions does not appear at angular momentum compensation temperature, which is different from the ferrimagnet domain wall. In addition, the skyrmion motion velocity and direction can be modulated by adjusting the net angular momentum density. The obtained results are useful for future experiment design and spintronic applications in ferrimagnets.image (c) 2024 WILEY-VCH GmbH