Ultrafast Electron Dynamics in Magnetic Thin Films

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.