Ultrafast magnetoacoustics in ferromagnetic and antiferromagnetic thin-film heterostructures

Excitation of coherent high-frequency magnons (quanta of spin waves) is critical to the development of high-speed magnonic devices. Here we computationally demonstrate the excitation of coherent terahertz (THz) magnons in ferromagnetic and antiferromagnetic thin films by a photoinduced picosecond acoustic pulse. Analytical calculations are performed to reveal the magnon excitation mechanism. Through spin pumping and spin-charge conversion, these magnons can inject THz charge current into an adjacent heavy-metal film which in turn emits electromagnetic (EM) waves. Based on dynamical phase-field simulations, we show that the emitted EM wave retains the spectral information of all the magnon modes, providing a basis for detection via THz emission spectroscopy.