Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin–phonon interactions
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Abstract
Antiferromagnetic materials have been proposed as new types of narrowband
THz spintronic devices owing to their ultrafast spin dynamics. Manipulating
coherently their spin dynamics, however, remains a key challenge that is
envisioned to be accomplished by spin-orbit torques or direct optical excita tions. Here, we demonstrate the combined generation of broadband THz
(incoherent) magnons and narrowband (coherent) magnons at 1 THz in low
damping thin films of NiO/Pt. We evidence, experimentally and through
modeling, two excitation processes of spin dynamics in NiO: an off-resonant
instantaneous optical spin torque in (111) oriented films and a strain-wave induced THz torque induced by ultrafast Pt excitation in (001) oriented films.
Both phenomena lead to the emission of a THz signal through the inverse spin
Hall effect in the adjacent heavy metal layer. We unravel the characteristic
timescales of the two excitation processes found to be < 50 fs and > 300 fs,
respectively, and thus open new routes towards the development of fast opto spintronic devices based on antiferromagnetic materials.
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Nature Communications, 14, Nature Publishing Group UK, London, 2023, https://doi.org/10.1038/s41467-023-37509-6