Fig. 2.

Magnetoelastic excitation in garnet films. (A) Impulsive Raman process induced by an ultrafast laser pulse. (B) Schematic dispersions of phonons and a spin wave in an iron garnet film with anticrossings via magnetoelastic interactions. (C) Faraday microscopy snapshots on the generation and propagation of magnetoelastic waves. The pump laser pulse (1,300 nm, 100 nJ) excites the longitudinal (LA) and transverse (TA) acoustic phonons coupled to the spin moments via the magnetoelastic interaction, leading to the Faraday rotation of the probe light (800 nm) arriving at the specified elapsed time. Corresponding wave modes in the dispersion relations are indicated by dotted arrows from B. The images were acquired with exposure time of 120 s under an in-plane magnetic field of 700 G applied along the x axis. (D) Simulations of the magnetoelastic action to the spin moments (as represented by $m_z$ induced by TA and LA phonons). Orange and green belts stand for the assumed plus/minus phonon magnitude, with the lattice displacement along the z axis for the TA phonon and along the propagation direction in the $xy$ plane for the LA phonon.