Normal mode splitting in interacting arrays of cylindrical permalloy dots

Abstract

Brillouin light scattering has been exploited to study the dependence of the spin-wave spectrum on the interdot distance in squared arrays of circular permalloy dots with radius R=100nm, thickness L=50nm, and interdot spacing (s) variable in the range between 50 and 800nm. The experimental data have been satisfactorily reproduced using a micromagnetic approach which solves the discretized Landau-Lifshitz-Gilbert equation over a 3×3 matrix of differently spaced circular dots and performing a local Fourier transform. This approach enabled us to clarify that, on reducing the s∕R ratio, some of the normal modes existing within each isolated dot increase their frequency retaining their own character. The fundamental mode, instead, splits into three modes characterized by different profiles of the dynamic magnetization. For all these modes, hybriditazion effects have also been observed.