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

## TL;DR

This paper demonstrates how dynamical magnetostatic coupling in a permalloy film with Ni stripes creates tunable magnonic band gaps and nonreciprocal spin wave propagation, offering new avenues for magnonic device design.

## Contribution

It introduces a novel method to induce and control magnonic band structures and nonreciprocity in homogeneous ferromagnetic films via periodic Ni stripes without complex nanofabrication.

## Key findings

- Magnonic band gaps are formed due to dynamical coupling with Ni stripes.
- Band gap width can be tuned by adjusting interlayer thickness.
- Nonreciprocal spin wave behavior is observed at the band edges.

## Abstract

An efficient way for the control of spin wave propagation in a magnetic medium is the use of periodic patterns known as magnonic crystals (MCs). However, the fabrication of MCs especially bi-components, with periodicity on 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 modified periodically surrounding. The structure is also suitable for exploiting nonreciprocal properties of the surface spin waves. In this work, we demonstrate that the magnonic band structure forms in thin permalloy film due to dynamical magnetostatic coupling with Ni stripes near its surface. We show, that the band gap width can be systematically tuned by the changing interlayer thickness between film and stripes. We show also the effect of nonreciprocity, which is seen at the band gap edge shifted from the Brillouin zone boundary and also in nonreciprocal interaction of propagating spin waves in Py film with the standing spin waves in Ni stripes. Our findings open possibility for further investigation and exploitation of the nonreciprocity and band structure in magnonic devices.

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Source: https://tomesphere.com/paper/1706.03202