Topological Magnetic Structures and Their Dynamics

The current-induced dynamics of magnetic structures is quite complex. For example, magnetic skyrmions allow for ‘banana kicks’ in magnetism, i.e., not only a motion of the skyrmions along but also transverse to the current direction. This effect, which has become known as the skyrmion Hall effect [1,2,3], is often disruptive for device applications. In this talk, we will present possibilities of how to eliminate the skyrmion Hall effect [4,5]. As a particular example, we discuss helical phases which provide confined one-dimensional channels for high-speed skyrmion motion. We discuss how skyrmions can be generated in such helical backgrounds and analyze their stability [6].<br/>Moreover, we will address the role played by topology in the physics of the skyrmion Hall effect. For example, it is widely believed that the skyrmion Hall effect, vanishes for overall topologically neutral structures such as (synthetic) antiferromagnetic skyrmions and skyrmioniums due to a compensation of Magnus forces. While this is true for spin-transfer torque-driven skyrmions, we show that this simple picture is generally false for spin-orbit torque-driven objects [7]. We find that the skyrmion Hall angle for spin-orbit torque-driven skyrmions is directly related to their helicity, which imposes an unexpected roadblock for developing faster and lower input racetrack memories based on spin-orbit torques.<br/><br/>[1] T. Schulz, et al., Nat. Phys. 8, 301 (2012)<br/>[2] K. Litzius, et al., Nat. Phys. 13, 170 (2017)<br/>[3] W. Jiang, et al., Nat. Phys. 13, 162 (2017)<br/>[4] R. Zarzuela, et al., Phys. Rev. B 101, 054405 (2020)<br/>[5] K.-W. Kim, et al., Phys. Rev. B 97, 224427 (2018)<br/>[6] R. Knapman, et al., J. Phys. D: Appl Phys. 54, 404003 (2021)<br/>[7] R. Msiska, et al., Phys. Rev. Appl. 17, 064015 (2022)