Spin-wave nonreciprocity and magnonic band structure in a thin permalloy film induced by dynamical coupling with an array of Ni stripes

An efficient way for control of the spin wave propagation in a magnetic medium is the use of periodic patterns known as magnonic crystals (MCs). However, the fabrication of MCs especially bicomponents, with periodicity in nanoscale, is a challenging task due to the requirement for sharp interfaces. An alternative method to circumvent this problem is to use homogeneous ferromagnetic film with a modified periodically surrounding. In this work we demonstrate that the magnonic band structure is formed in thin Py film due to dynamical magnetostatic coupling with the array of Ni stripes. We show that the band gap width can be systematically tuned by changing separation between film and stripes. We show also the effect of nonreciprocity, which is seen at the band gap edge which is shifted from the Brillouin zone boundary and also in nonreciprocal interaction of propagating spin waves in Py film with the standing waves in Ni stripes. Our findings open a possibility for further investigation and exploitation of the nonreciprocity and band structure in magnonic devices.