Spin wave dispersion and intensity correlation in width-modulated nanowire arrays: A Brillouin light scattering study

TL;DR

This study investigates how width modulation and relative displacement in nanowire arrays influence spin wave dispersion and intensity, revealing controllable magnonic properties via Brillouin light scattering and theoretical calculations.

Contribution

It demonstrates that the amplitude and frequency splitting of spin wave modes can be effectively tuned by adjusting the relative displacement of width-modulated nanowire sides.

Findings

Bloch-type spin wave modes observed

Mode splitting depends on relative displacement D

Magnonic band amplitude is controllable by D

Abstract

Using Brillouin light scattering spectroscopy and dynamical matrix method calculations, we study collective spin waves in dense arrays of periodically double-side width-modulated Permalloy nanowires. Width modulation is achieved by creating a sequence of triangular notches on the two parallel nanowire sides, with a periodicity of p=1000 nm, and tunable relative displacement (D) of the notches sequence on the two lateral sides. Both symmetric (D=0) and asymmetric (D= 250 and 500 nm) width-modulated nanowires were investigated. We have found that the detected modes have Bloch-type character and belong to a doublet deriving from the splitting of the modes characteristics of the nanowire with homogeneous width. Interestingly, the amplitude of the magnonic band, the frequency difference of the doublet, as well as their relative scattering intensity, can be efficiently controlled by increasing D rather than having single- or symmetric (D=0) double-side width-modulation.