Manipulating magnons via ultrafast magnetization modulation

We demonstrate how fundamental properties of magnons may be manipulated using femtosecond laser pulses by performing ab initio real-time time-dependent density functional theory simulations. To illustrate this, we show how the spin-wave dynamics in ${\mathrm{Fe}}₅₀{\mathrm{Ni}}₅₀$ can be manipulated in three different ways by tailoring the applied laser pulse to excite optically induced intersublattice transfer (OISTR): (1) element-selective destruction of magnon modes depending on the laser intensity, (2) delay-dependent freezing of the magnon mode into a transient noncollinear state (where the delay is in the pulse peak with respect to the start of simulations), and (3) OISTR-driven renormalization of the optical magnon frequency. Harnessing such processes would significantly speed up magnonic devices.