IEEE Magnetics Society and HKUST ECE Joint Distinguished Seminar - THz Spin Resonance and Magnon Currents in Antiferromagnetic Heterostructures

Magnons, the quasiparticles of spin waves, are the elementary low-energy collective excitations in magnetic materials. Antiferromagnetic insulators (AFMIs) can host THz frequency magnons to carry angular momentum without moving charges [1], however not much is known about the propagation of magnons in antiferromagnetic materials so far. We first detect THz spin resonance in an antiferromagnetic materials such as NiO [2] and Fe2O3 [3]. Using current injection in antiferromagnetic heterostructures with a heavy metal, we manipulate the magnon frequency, enabling high-speed and low-dissipation operation of spin devices [2,4]. The magnon propagation speed, which is a key parameter to determine data operation time, remains elusive in AFMIs, particularly at nanometer distances due to the lack of sufficiently fast probes. Using the direct time-domain measurement of the velocity of antiferromagnetic magnons in NiO, we find the magnons propagate in NiO at a superluminal velocity up to 650 km/s [5]. Our observation suggests the prospects of energy-efficient nanodevices using AFMIs considering finite dissipation in real materials.

[1] Wang, Y. et al., Science 366, 1125 (2019); [2] Yang, D. et al., Phys. Rev. Applied. 20, 014023 (2023); [3] Liu, Q. et al., Adv. Funct. Mater. 2305173 (2023); [4] Yang, D. et al., Nat. Comm. 15, 4046 (2024); [5] Lee, K. et al., Nat. Nanotechnol. 16, 1337 (2021)