Ultrafast Time-Resolved Demagnetization Imaging in a Ferromagnet

Ultrashort laser pulses have proven to be invaluable tools for studying the out of equilibrium magnetic properties of matter [1]. Significant interest has been directed toward understanding the temporal evolution and manipulation of the magnetization vector <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\vec{M}$</tex> in ferromagnets. Pump-probe schemes have been extensively employed in the last twenty years to detect the impulsive changes in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\vec{M}$</tex> induced by light and to track its dynamics with femtosecond resolution [2]. However, relatively few studies have explored the spatial dependence of light-induced demagnetization. These studies have predominantly utilized either point-scanning techniques [3] or a combination of polarization optics and CCD cameras [4]. In this work, we leverage the capabilities of a self-referencing ultrafast holographic microscope [5], [6] to image the spatio-temporal dynamics of the light-induced demagnetization in a Pt/CoFeB/MgO structure with 100-fs and sub-μm resolution.