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 (THz) pump–optical probe setup to measure structural features in the ultrafast time scale. We find that complete demagnetization is possible with <6 THz pulses. This occurs concurrently with longitudinal acoustic phonons and an electronic response.
Highlights
The study of ultrafast magnetism is crucial in advancing our understanding of magnetic systems, as well as developing ultrafast memory devices
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
As an example, when a ferromagnetic film is excited by a femtosecond laser pulse, partial demagnetization of the material occurs within ∼100 fs, followed by a remagnetisation to the original state on a longer time scale
Summary
The study of ultrafast magnetism is crucial in advancing our understanding of magnetic systems, as well as developing ultrafast memory devices. The difficulty of this subject lies in spin dynamics, and its role as a part of a larger picture of the barely understood coupled structural dynamics. As an example, when a ferromagnetic film is excited by a femtosecond (fs) laser pulse, partial demagnetization of the material occurs within ∼100 fs, followed by a remagnetisation to the original state on a longer time scale This was first observed in 1996 for optical laser pulses [1], and later for THz laser pulses [2,3,4,5]. It is essential to understand the physical mechanisms that can influence the spin angular momenta of the electrons responsible for magnetisation
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