Antiferromagnetic spintronics is an emerging research field which aims to utilize antiferromagnets as core elements in spintronic devices1,2. A central motivation towards this direction is that antiferromagnetic spin dynamics is expected to be much faster than its ferromagnetic counterpart3. Recent theories indeed predicted faster dynamics of antiferromagnetic domain walls (DWs) than ferromagnetic DWs4,5,6. However, experimental investigations of antiferromagnetic spin dynamics have remained unexplored, mainly because of the magnetic field immunity of antiferromagnets7. Here we show that fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnets at the angular momentum compensation point TA. Using rare earth–3d-transition metal ferrimagnetic compounds where net magnetic moment is nonzero at TA, the field-driven DW mobility is remarkably enhanced up to 20 km s−1 T−1. The collective coordinate approach generalized for ferrimagnets8 and atomistic spin model simulations6,9 show that this remarkable enhancement is a consequence of antiferromagnetic spin dynamics at TA. Our finding allows us to investigate the physics of antiferromagnetic spin dynamics and highlights the importance of tuning of the angular momentum compensation point of ferrimagnets, which could be a key towards ferrimagnetic spintronics.
This work was partly supported by JSPS KAKENHI Grant Numbers 15H05702, 26870300, 26870304, 26103002, 25220604, 2604316 Collaborative Research Program of the Institute for Chemical Research, Kyoto University, the Cooperative Research Project Program of the Research Institute of Electrical Communication, Tohoku University, and R&D project for ICT Key Technology of MEXT from the Japan Society for the Promotion of Science (JSPS). K.-J.K. was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (No. 2017R1C1B2009686, NRF-2016R1A5A1008184) and by the DGIST R&D Program of the Ministry of Science, ICT and Future Planning (17-BT-02). S.K.K. and Y.T. acknowledge support from the Army Research Office under Contract No. W911NF-14-1-0016. D.-H.K. was supported by an Overseas Researcher under Postdoctoral Fellowship of JSPS (Grant Number P16314). K.-J.L. acknowledges support from the National Research Foundation of Korea (NRF-2015M3D1A1070465, NRF-2017R1A2B2006119).