Near- and mid-infrared excitation of ultrafast demagnetization in a cobalt multilayer system

TL;DR

This study demonstrates that ultrafast demagnetization in a cobalt multilayer can be efficiently induced across a broad spectral range from near-IR to mid-IR, primarily influenced by the pulse profile rather than wavelength.

Contribution

It reveals that the demagnetization dynamics are largely independent of excitation wavelength, emphasizing the importance of pulse temporal profile over spectral properties.

Findings

Efficient demagnetization occurs across 0.8 to 8.7 μm wavelengths.

Demagnetization dynamics are minimally dependent on excitation wavelength.

Pulse temporal profile significantly influences ultrafast demagnetization.

Abstract

In the last few decades, ultrafast demagnetization elicited by ultrashort laser pulses has been the subject of a large body of work that aims to better understand and control this phenomenon. Although specific magnetic materials' properties play a key role in defining ultrafast demagnetization dynamics, features of the driving laser pulse such as its duration and photon energy might also contribute. Here, we report ultrafast demagnetization of a cobalt/platinum multilayer in a broad spectral range spanning from the near-infrared (near-IR) to the mid-infrared (mid-IR), with wavelengths between 0.8 and 8.7 $\mu$m. The ultrafast dynamics of the macroscopic magnetization is tracked via the time-resolved magneto-optical Kerr effect. We show that the ultrafast demagnetization of the sample can be efficiently induced over that entire excitation spectrum with minimal dependence on the excitation wavelength. Instead, we confirm that the temporal profile of the pump excitation pulse is an important factor influencing ultrafast demagnetization dynamics.