Forward mode coupling and bandgap formation in magnonic crystals

The bandgap formation for magnetostatic surface spin waves (MSSWʼs) is numerically simulated in a lateral magnetic superlattice. It is found that, while the bandgaps opened at Brillouin zone edges is an intrinsic property of the periodic lattice, the exact mechanism of their formation can be revealed by incorporating a real source of MSSW excitation into the system. The obtained results uncover that the bandgaps arise due to the coupling between the MSSWʼs travelling away from the excitation source (forward modes). This behavior differs from that provided by Bragg diffraction, which is the well-established mechanism for bandgap formation in periodic lattices.