  Advanced magnetic recording paradigms typically use large temperature changes
to drive switching which is detrimental to device longevity, hence finding
non-thermal routes is crucial for future applications. By employing atomistic
spin-lattice dynamics simulations, we show efficient coherent magnetisation
switching triggered by THz phonon excitation in insulating single species
materials. The key ingredient is excitation near the $P$-point of the spectrum
in conditions where spins typically cannot be excited and when manifold $k$
phonon modes are accessible at the same frequency. Our model predicts the
necessary ingredients for low-dissipative switching and provides new insight
into THz-excited spin dynamics.
