Phononic and magnonic dispersions of surface waves on a permalloy/BARC nanostructured array

Huihui Pan,Hock Siah Lim,Vanessa Li Zhang,Kai Di,Ser Choon Ng,Adekunle Olusola Adeyeye,Meng Hau Kuok,Navab Singh

doi:10.1186/1556-276x-8-115

Abstract

Phononic and magnonic dispersions of a linear array of periodic alternating Ni80Fe20 and bottom anti-reflective coating nanostripes on a Si substrate have been measured using Brillouin light scattering. The observed phononic gaps are considerably larger than those of laterally patterned multi-component crystals previously reported, mainly a consequence of the high elastic and density contrasts between the stripe materials. Additionally, the phonon hybridization bandgap has an unusual origin in the hybridization and avoided crossing of the zone-folded Rayleigh and pseudo-Sezawa waves. The magnonic band structure features near-dispersionless branches, with unusual vortex-like dynamic magnetization profiles, some of which lie below the highly-dispersive fundamental mode branch. Finite element calculations of the phononic and magnonic dispersions of the magphonic crystal accord well with experimental data.

Highlights

Photonic-phononic crystals, referred to as phoxonic crystals [1,2,3,4], are of great interest as their dual photonic and phononic bandgaps allow the simultaneous control of photon and phonon propagation in these crystals
The measured phononic dispersion spectrum features a 1.0-GHz gap opening centered at 4.8 GHz at the Brillouin zone boundary, and a 2.2-GHz bandgap centered at 6.5 GHz
The 350-nm-wide computational cell used comprises a 63-nm-thick layer of a 100-nm-wide bottom anti-reflective coating (BARC) stripe sandwiched between two 125-nm-wide Py stripes, atop a 2-μm-thick Si substrate, with its bottom boundary fixed

Summary

Introduction

Photonic-phononic crystals, referred to as phoxonic crystals [1,2,3,4], are of great interest as their dual photonic and phononic bandgaps allow the simultaneous control of photon and phonon propagation in these crystals Another class of metamaterials possessing dual-excitation bandgaps is magnonic-phononic or magphonic crystals [5,6,7]. Less well known than phoxonic materials, they too have promising application potential because of the possibility of the simultaneous control and manipulation of magnon and phonon propagation in them They are potentially more useful technologically than either solely magnonic or phononic crystals which depend on a single type of excitation, namely magnons or phonons, as the respective information carrier. Zhang et al experimentally studied these materials in the form of a two-dimensional (2D) chessboard-patterned array of cobalt and Ni80Fe20

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