Spin wave surface states in one-dimensional planar magnonic crystals

TL;DR

This paper explores surface spin wave states in one-dimensional planar magnonic crystals, comparing exchange and dipolar regimes, and highlights the importance of surface anisotropy and dipolar effects for their existence.

Contribution

It demonstrates the analog between anisotropy-modulated magnonic crystals and electronic crystals, and analyzes the influence of dipolar interactions on surface states.

Findings

Surface states exist in both exchange and dipolar regimes.

Tuning surface anisotropy or dipolar effects is crucial for surface state existence.

Surface states in dipolar regime differ from electronic crystals due to long-range interactions.

Abstract

We have investigated surface spin wave states in one-dimensional planar bi-component magnonic crystals, localized on the surfaces resulting from the breaking of the periodic structure. The two systems have been considered: the magnonic crystal with periodic changes of the anisotropy field in exchange regime and the magnonic crystal composed of Fe and Ni stripes in dipolar regime with exchange interactions included. We chose the symmetric unit cell for both systems to implement the symmetry related criteria for existence of the surface states. We investigated also the surface states induced by the presence of perturbation of the surface areas of the magnonic crystals. We showed, that the system with modulated anisotropy is a direct analog of the electronic crystal. Therefore, the surface states in both systems have the same properties. For surface states existing in magnonic crystals in dipolar regime we demonstrated that spin waves preserve distinct differences to the electronic crystals, which are due to long-range dynamic dipolar interactions. We found that tuning of the strength of magnetization pinning resulting from the surface anisotropy or dipolar effect is vitally important for existence of the surface states in magnonic crystals.