Fig. 1: Ultrafast magnetoacoustics in FM thin films.

a Schematic of Al/MAO/MAFO/Pt heterostructure as an example for acoustic excitation of sub-THz magnons in a FM thin film and their detection via electromagnetic (EM) wave emission. The magnons (denoted by Δm) of different modes n are excited in the MAFO layer by fs-laser-induced ultrashort acoustic pulse εzz which has a peak amplitude εmax and a duration τ. The excited magnons pump spin current Js into the Pt layer, which is converted to transverse charge current Jc via iSHE. Jc emits EM wave via electric dipole radiation. b Analytically calculated frequencies of the n = 1 and n = 2 mode magnons and the ferromagnetic resonance (FMR) mode (n = 0) magnon as a function of MAFO film thickness (d). The frequencies for the case of d = 15 nm are labeled.