Spin-wave dynamics in Permalloy/Cobalt magnonic crystals in the presence of a non-magnetic spacer

TL;DR

This study explores how inserting a non-magnetic spacer in bi-component magnonic crystals alters spin wave dispersion, enabling control over magnonic band structures and edge modes, with implications for designing advanced magnonic devices.

Contribution

It demonstrates that non-magnetic spacers significantly modify magnetic fields and band structures, allowing manipulation of edge-localized spin wave modes in bi-component magnonic crystals.

Findings

Non-magnetic spacers alter internal magnetic fields at edges.

Edge modes are influenced by spacer-induced field changes.

Magnonic band structure can be engineered with spacers.

Abstract

In this paper, we theoretically study the influence of a non-magnetic spacer between ferromagnetic dots and ferromagnetic matrix on the frequency dispersion of the spin wave excitations in two-dimensional bi-component magnonic crystals. By means of the dynamical matrix method we investigate structures inhomogeneous across the thickness represented by square arrays of Cobalt or Permalloy dots in a Permalloy matrix. We show that the introduction of a non-magnetic spacer significantly modifies the total internal magnetic field especially at the edges of the grooves and dots. This permits the manipulation of the magnonic band structure of spin waves localized either at the edges of the dots or in matrix material at the edges of grooves. According to the micromagnetic simulations two types of end modes were found. The corresponding frequencies are significantly influenced by the end modes localization region. We also show that, with the use of a single ferromagnetic material, it is possible to design a magnonic crystal preserving properties of bi-component magnonic crystals and magnonic antidot lattices. Finally, the influence of the non-magnetic spacers on the technologically relevant parameters like group velocity and magnonic band width are discussed.