Domain wall dynamics in metallic and insulating ferrimagnets*

In ferromagnet systems, engineered interfaces can give rise to the chiral Dzyaloshinskii-Moriya interaction (DMI) in otherwise symmetric systems¹. Research has primarily focused on the study of chiral solitons in metallic systems, where heavy metal underlayers provide a large spin-orbit torque and an interfacial DMI. This resulted in extensive research of chiral solitons in ferromagnetic systems^1,2. However, damping in metals is generally high, which limits soliton mobility. The low damping and ferrimagnetic dynamics of insulating garnets make them ripe candidates for ultrafast spin textures. Moreover, spin-orbit effects and spin-transport phenomenon from adjacent heavy metal layers have been used to manipulate the magnetisation in these materials³. Here, we use a pure spin current from an adjacent Pt overlayer to characterise chiral domain wall motion and DMI in epitaxial iron garnet films with perpendicular magnetic anisotropy. We use the significant interfacial DMI and a large spin-orbit torque to drive chiral domain walls to record velocities of a few thousand meters per second.
1 Emori, S. et al. Nat. Mater. 12, 611–616 (2013)
2 Woo, S. et al. Nat. Mater. 15, 501–506 (2016)
3 Avci, C. O. et al. Nat. Mater. 16, 309–314 (2017)