Detection of picosecond magnetization dynamics of 50 nm magnetic dots down to the single dot regime

TL;DR

This study demonstrates all-optical detection of picosecond magnetization dynamics in 50 nm Ni80Fe20 nanodots, revealing mode behavior and interaction effects down to the single-dot regime.

Contribution

It provides the first all-optical measurement of magnetization dynamics in individual 50 nm nanodots and explores how array density influences these dynamics.

Findings

Single nanodots exhibit a dominant edge mode with higher damping.

Increasing array density enhances precession frequency and damping.

Mode splitting and damping jumps occur at 50 nm edge-to-edge separation.

Abstract

We report an all-optical time-domain detection of picosecond magnetization dynamics of arrays of 50 nm Ni80Fe20 (permalloy) dots down to the single nanodot regime. In the single nanodot regime the dynamics reveals one dominant resonant mode corresponding to the edge mode of the 50 nm dot with slightly higher damping than that of the unpatterned thin film. With the increase in areal density of the array both the precession frequency and damping increases significantly due to the increase in magnetostatic interactions between the nanodots and a mode splitting and sudden jump in apparent damping are observed at an edge-to-edge separation of 50 nm.