Longitudinal evolution of magnetization of ferromagnets following ultrafast demagnetization: Role of finite size and shape of demagnetized region

TL;DR

This paper investigates how the shape and size of a demagnetized region influence the relaxation dynamics of ferromagnets after ultrafast demagnetization, highlighting the significant role of wave front motion.

Contribution

It demonstrates the shape-dependent relaxation rates in ferromagnets post-ultrafast demagnetization, emphasizing the impact of wave front motion in different geometries.

Findings

Shape of demagnetized region affects relaxation rate.

Wave front motion enhances relaxation in spherical and cylindrical geometries.

Effect observable with femtosecond laser pulses.

Abstract

A dependence of a relaxation rate on the shape of the demagnetized region for a longitudinal evolution of total magnetization to its equilibrium value following the ultrafast demagnetization is demonstrated. This shape-dependence is caused by a motion of the wave front inside the demagnetized region. The contribution of the wave front for spherically symmetric shape of the demagnetized region is up to 3 times and for cylindrically symmetric shape up to 2 times stronger than for one dimensional demagnetized region. This effect can be observed after the demagnetization by a tightly focused femtosecond laser pulse.