Magnon spectrum in Ferromagnet-Superconductor heterostructure

Research on ferromagnet-superconductor heterostructures gives rise to novel quantum phases and excitations. Spin-waves (Magnons) can propagate in a ferromagnetic thin film while magnetic fields penetrate through a type-II superconducting thin film forming a vortex lattice. Here, we study the magnon spectrum in ferromagnetic thin films in the presence of a vortex lattice in a superconducting thin film separated by an insulating film. It was revealed that the spin-waves interact with the vortex lattice and the magnon spectrum is modified. Because of the periodic modulation of the magnetic field from the vortex lattice, the ferromagnetic film influenced by the vortex lattice acts as a magnonic crystal and results in the formation of bandgaps in the spin wave spectrum. The vortex lattice depends on the magnitude of the applied magnetic field, which can then be used to tune the spin wave band gaps for possible magnonic applications.