Engineering strong magnon–phonon coupling in single CoFe nanomagnets

Hybrid magnonic systems are promising platforms for quantum technologies, leveraging coherent coupling between magnons and phonons. Here, we demonstrate strong magnon–phonon coupling in CoFe nanomagnets, a material with high magnetostriction. Using time-resolved magneto-optical Kerr effect spectroscopy, we demonstrate strong coupling between magnonic and phononic modes in both polycrystalline and single-crystalline CoFe nanomagnets. Our findings reveal strong coupling with cooperativity values of C=20.04 for a polycrystalline CoFe nanomagnet and C=37.94 for a single-crystalline CoFe nanomagnet. The enhanced coupling strength in the single-crystalline CoFe nanomagnet is attributed to the higher magnetostriction in CoFe systems and lower intrinsic magnetic damping. This work highlights the critical role of material properties and crystalline structures in optimizing hybrid magnon–phonon systems for miniaturized quantum applications.