The building blocks of magnonics

TL;DR

This review explores the design and control of spin-wave propagation in magnetic metamaterials, emphasizing their potential for dynamic waveguides, switches, and computing, with a focus on localization, delocalization, and femtosecond laser control.

Contribution

It introduces novel concepts for manipulating spin-wave modes in magnetic metamaterials and discusses the role of femtosecond lasers in controlling localization and delocalization.

Findings

Magnetic metamaterials can be tailored to control spin-wave band structures.

Localized and delocalized spin-wave modes can be manipulated using femtosecond laser techniques.

Potential for spin-wave based computing and dynamic waveguides is demonstrated.

Abstract

Novel material properties can be realized by designing waves' dispersion relations in artificial crystals. The crystal's structural length scales may range from nano- (light) up to centimeters (sound waves). Because of their emergent properties these materials are called metamaterials. Different to photonics, where the dielectric constant dominantly determines the index of refraction, in a ferromagnet the spin-wave index of refraction can be dramatically changed already by the magnetization direction. This allows a different flexibility in realizing dynamic wave guides or spin-wave switches. The present review will give an introduction into the novel functionalities of spin-wave devices, concepts for spin-wave based computing and magnonic crystals. The parameters of the magnetic metamaterials are adjusted to the spin-wave k-vector such that the magnonic band structure is designed. However, already the elementary building block of an antidot lattice, the singular hole, owns a strongly varying internal potential determined by its magnetic dipole field and a localization of spin-wave modes. Photo-magnonics reveal a way to investigate the control over the interplay between localization and delocalization of the spin-wave modes using femtosecond lasers, which is a major focus of this review. We will discuss the crucial parameters to realize free Bloch states and how, by contrast, a controlled localization might allow to gradually turn on and manipulate spin-wave interactions in spin-wave based devices in the future.