Magnon-phonon Fermi resonance in antiferromagnetic CoF<sub>2</sub>.

Metzger, Thomas W J; Grishunin, Kirill A; Reinhoffer, Chris; Dubrovin, Roman M; Arshad, Atiqa; Ilyakov, Igor; de Oliveira, Thales V A G; Ponomaryov, Alexey et al. · Nat Commun · 2024

basic_science · Level V

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Abstract

Understanding spin-lattice interactions in antiferromagnets is a critical element of the fields of antiferromagnetic spintronics and magnonics. Recently, coherent nonlinear phonon dynamics mediated by a magnon state were discovered in an antiferromagnet. Here, we suggest that a strongly coupled two-magnon-one phonon state in this prototypical system opens a novel pathway to coherently control magnon-phonon dynamics. Utilizing intense narrow-band terahertz (THz) pulses and tunable magnetic fields up to μ<sub>0</sub>H<sub>ext</sub> = 7 T, we experimentally realize the conditions of magnon-phonon Fermi resonance in antiferromagnetic CoF<sub>2</sub>. These conditions imply that both the spin and the lattice anharmonicities harvest energy from the transfer between the subsystems if the magnon eigenfrequency f<sub>m</sub> is half the frequency of the phonon 2f<sub>m</sub> = f<sub>ph</sub>. Performing THz pump-infrared probe spectroscopy in conjunction with simulations, we explore the coupled magnon-phonon dynamics in the vicinity of the Fermi-resonance and reveal the corresponding fingerprints of nonlinear interaction facilitating energy exchange between these subsystems.