All-Optical Excitation and Detection of Picosecond Dynamics of Ordered Arrays of Nanomagnets with Varying Areal Density

TL;DR

This study uses all-optical time-resolved Kerr microscopy to investigate the collective magnetic dynamics in nanomagnet arrays with varying densities, revealing distinct regimes of uniform, nonuniform, and noncollective behavior.

Contribution

It introduces a precise optical method to characterize and distinguish different collective regimes in nanomagnet arrays based on areal density.

Findings

High density arrays show a single uniform mode.

Intermediate densities exhibit three nonuniform modes.

Low density arrays display noncollective dynamics.

Abstract

We have demonstrated optical excitation and detection of collective precessional dynamics in arrays of coupled Ni80Fe20 (permalloy) nanoelements with systematically varying areal density by an all-optical time-resolved Kerr microscope. We have applied this technique to precisely determine three different collective regimes in these arrays. At very high areal density, a single uniform collective mode is observed where the edge modes of the constituent elements are suppressed. At intermediate areal densities, three nonuniform collective modes appear and at very low areal density, we observe noncollective dynamics and only the centre and edge modes of the constituent elements appear.