Ultrafast Electron Dynamics in Magnetic Thin Films

TL;DR

This paper demonstrates that ultrafast demagnetisation in magnetic thin films can be achieved using low-fluence, long-wavelength terahertz pulses, revealing a new method to control spin order without high-energy lasers.

Contribution

It introduces a terahertz pump optical probe technique to induce and study ultrafast demagnetisation, showing that low-energy pulses can effectively manipulate magnetic states.

Findings

Complete demagnetisation occurs with <6 THz pulses.

Demagnetisation is concurrent with phonon and electronic responses.

Low fluence is sufficient for full demagnetisation, eliminating need for high-power lasers.

Abstract

In past decades, ultrafast spin dynamics in magnetic systems have been associated with heat deposition from high energy laser pulses, limiting the selective access to spin order. Here we use a long wavelength terahertz pump optical probe setup to measure structural features in the ultrafast time scale. We find that complete demagnetisation is possible with <6 THz pulses. This occurs concurrently with longitudinal acoustic phonons and an electronic response, followed by the magnetic response. The required fluence for full demagnetisation is low, ruling out the necessity of a high power light source.