  Understanding spin-lattice coupling represents a key challenge in modern
condensed matter physics, with crucial importance and implications for
ultrafast and 2D-magnetism. The efficiency of angular momentum and energy
transfer between spins and the lattice imposes fundamental speed limits on the
ability to control spins in spintronics, magnonics and magnetic data storage.
We report on an efficient nonlinear mechanism of spin-lattice coupling driven
by THz light pulses. A nearly single-cycle THz pulse resonantly interacts with
a coherent magnonic state in the antiferromagnet CoF2 and excites the
Raman-active THz phonon. The results reveal the unique functionality of
antiferromagnets allowing ultrafast spin-lattice coupling using light.
