  Dynamical backaction resulting from radiation pressure forces in
optomechanical systems has proven to be a versatile tool for manipulating
mechanical vibrations. Notably, dynamical backaction has resulted in the
cooling of a mechanical resonator to its ground-state, driving phonon lasing,
the generation of entangled states, and observation of the optical-spring
effect. In certain magnetic materials, mechanical vibrations can interact with
magnetic excitations (magnons) via the magnetostrictive interaction, resulting
in an analogous magnon-induced dynamical backaction. In this article, we
directly observe the impact of magnon-induced dynamical backaction on a
spherical magnetic sample's mechanical vibrations. Moreover, dynamical
backaction effects play a crucial role in many recent theoretical proposals;
thus, our work provides the foundation for future experimental work pursuing
many of these theoretical proposals.
