Sculpting Spin-Wave Landscapes via Curvature of 2D Magnonic Crystals

TL;DR

This paper demonstrates a novel method to engineer spin-wave dispersion in magnonic crystals using 3D curvilinear nanotemplates, enabling controlled band gaps and localized modes without material removal.

Contribution

The authors introduce a technique to manipulate demagnetizing fields via 3D nanotemplates, creating tunable spin-wave band gaps in continuous films, advancing magnonic device design.

Findings

Complete in-plane band gap observed in Permalloy films on 3D templates.

Flat-band modes exhibit strong real-space localization.

External magnetic field can open and close the spin-wave gap.

Abstract

Engineering the dispersion relation is one of the key ingredients enabling the application of spin waves in computational elements. One way to engineer the spin-wave band structure is to create an artificial magnonic crystal, which can be used to design specific band gaps or dispersion branches. However, creating a two-dimensional magnonic crystal usually requires removing material, which dramatically decreases the decay lengths of spin waves. Here, we present a method to manipulate the demagnetizing field landscape by utilizing large-area curvilinear nanotemplates consisting of three-dimensional nanopyramids arranged in a square lattice with a period of 400 nm. In a 50-nm-thick Permalloy film grown on these curvilinear templates, we experimentally observe a complete in-plane band gap together with flat-band modes that exhibit strong real-space localization of the spin waves in the pyramid valleys. Micro-focused Brillouin light scattering measurements corroborate the numerically predicted dispersion and reveal the possibility of opening and closing this gap by varying the external magnetic field. Our results establish three-dimensional-templated continuous films as a versatile platform for two-dimensional signal processing and magnonic computing elements.