Fig. 1: The pathway to magnon-phonon Fermi resonance.
From: Magnon-phonon Fermi resonance in antiferromagnetic CoF2
a Frequency tuning of the fundamental magnon frequency f0 and double frequency 2f0 by an external magnetic field μ0Hext applied along the antiferromagnetic easy axis of CoF2. The Fermi resonance matching condition 2fm = fph at the crossing of the double magnon frequency (red) and the phonon frequency (blue) is marked by a black star. Blue dots and red rectangles correspond to real experimental data points. b Graphical illustration of the nonlinear magnon-phonon dynamics. If the magnon frequency is f0, a THz pump pulse exclusively populates the magnon state. However, by tuning the resonance condition by an external magnetic field, for 2fm = fph, the magnon-phonon Fermi resonance condition is fulfilled and a channel of nonlinear energy transfer opens. c Feynman diagrams illustrating the processes of energy transfer involving two magnons and one phonon. Two magnon-phonon confluence (left) and phonon-two magnon splitting (right).
