Rongione, E.; Gueckstock, O.; Mattern, M.; Gomonay, O.; Meer, H.; Schmitt, C.; Ramos, R.; Kikkawa, T.; Micica, M.; Saitoh, E.; Sinova, J.; Jaffrès, H.; Mangeney, J.; Goennenwein, S.T.B.; Geprägs, S.; Kampfrath, T.; Kläui, M.; Bargheer, M.; Seifert, T.S.; Dhillon, S.; Lebrun, R.: Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin-phonon interactions. Nature Communications 14 (2023), p. 1818/1-8
10.1038/s41467-023-37509-6
Open Access Version
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 excitations. 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.