Actuation, propagation, and detection of transverse magnetoelastic waves in ferromagnets

• Acoustic waves can be used to excite spin waves via magnetoelastic coupling.
• Acoustic and spin waves in a ferromagnet are highly mixed close to the FMR frequency.
• Magneto-elastic waves allow for DC and AC spin current pumping acoustically.

We study propagation of ultrasonic waves through a ferromagnetic medium with special attention to the boundary conditions at the interface with an ultrasonic actuator. In analogy to charge and spin transport in conductors, we formulate the energy transport through the system as a scattering problem. We find that the magneto-elastic coupling leads to a non-vanishing magnetic (elastic) energy accompanying the acoustic (spin) waves with a resonantly enhanced effect around the anti-crossing in the dispersion relations. We demonstrate the physics of excitating magnetization dynamics via acoustic waves injected around the ferromagnetic resonance frequency.