Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

Abstract

X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L(3,2)-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.

Ultrafast demagnetization of Pt magnetic moment in L10-FePt probed by magnetic circular dichroism at a hard x-ray free electron laser

“…Thus far, the L (2p→5d) edge of 5d transition metals, which lies in the hard x-ray region, could not be used for trXMCD, and therefore the elementspecific spin dynamics of ferromagnetic materials with Pt have not yet been clarified. X-ray free electron lasers (XFELs) have recently enabled time-resolved measurements of ultrafast phenomena with ultrashort x-ray pulses with a duration of 100 fs < [22,23] and have been applied to various research fields including magnetization dynamics [24,25] and the dynamics of a 5d antiferromagnetic material observed by diffraction at an antiferromagnetic Bragg peak [26]. In this study, we report the first hard x-ray trXMCD measurements of the spin dynamics of the Pt moment in FePt using the XFEL with an x-ray phase retarder to produce circular polarized x-rays [27].…”

Photoinduced molecular chirality probed by ultrafast resonant X-ray spectroscopy

“…Measuring chirality specific signals requires an optical pump and a X-ray probe setup 8 with circularly polarized laser light. Such pulses are now available at facilities like the Stanford Linear Accelerator Center 9 or the Fermi free electron laser at Elettra Sincrotrone Trieste 10 . Circularly polarized X-ray pulses can utilize the element and orbital specificity of X-ray transitions to probe the matter chirality thus providing new local windows into molecular geometry changes.…”

Photon Beam Transport and Scientific Instruments at the European XFEL

“…Time-resolved resonant spectroscopy offers element-, site-, orbital-, and spin-selective probing of complex material dynamics that is either directly related to or indirectly coupled to the valence electrons. Physical properties such as oxidation state, magnetism, local symmetries and ordering as well as elementary excitations can be investigated using X-ray Absorption Spectroscopy (XAS) [86,89], X-ray Resonant Diffraction (XRD) [81][82][83] and Resonant Inelastic X-ray Scattering (RIXS) [87]. A particular aim of the SCS instrument is to combine these powerful spectroscopic techniques with X-ray diffraction and microscopy methods, which provide nanometer spatial-and femtosecond time resolutions.…”