N\'eel Spin Orbit Torque driven antiferromagnetic resonance in Mn2Au probed by time-domain THz spectroscopy
Abstract
We observe the excitation of collective modes in the THz range driven by the recently discovered N\'eel spin-orbit torques (NSOT) in the metallic antiferromagnet Mn2Au. Temperature dependent THz spectroscopy reveals a strong absorption mode centered near 1 THz, which upon heating from 4 K to 450 K softens and looses intensity. Comparison with the estimated eigenmode frequencies implies that the observed mode is an in-plane antiferromagnetic resonance (AFMR) mode. The AFMR absorption strength exceeds those found in antiferromagnetic insulators, driven by the magnetic field of the THz radiation, by three orders of magnitude. Based on this and the agreement with our theory modelling, we infer that the driving mechanism for the observed mode is the current induced NSOT. This electric manipulation of the Ne\'el order parameter at high frequencies makes Mn2Au a prime candidate for AFM ultrafast memory applications.
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