  We theoretically study the electromagnetic wave radiation of magnons driven
by acoustic phonons in systems with strong magnon-phonon interaction. We
evaluate the field dependence of radiation intensity spectra which exhibits the
avoided crossing, a characteristic of strongly coupled systems. At the
crossover where the magnon and phonon eigenstates are hybridized, we
demonstrate the existence of two resonant radiation frequencies with circular
polarization and the enhancement of antenna radiation efficiency by over 100
times. Our results open up possibilities of developing ultra-compact antennas
by using the hybridized magnon-phonon mode.
