Single shot time-resolved magnetic x-ray absorption at a Free Electron Laser

Abstract

Ultrafast dynamics are generally investigated using stroboscopic pump-probe measurements, which characterize the sample properties for a single, specific time delay. These measurements are then repeated for a series of discrete time delays to reconstruct the overall time trace of the process. As a consequence, this approach is limited to the investigation of fully reversible phenomena. We recently introduced an off-axis zone plate based X-ray streaking technique, which overcomes this limitation by sampling the relaxation dynamics with a single femtosecond X-ray pulse streaked over a picosecond long time window. In this article we show that the X-ray absorption cross section can be employed as the contrast mechanism in this novel technique. We show that changes of the absorption cross section on the percent level can be resolved with this method. To this end we measure the ultrafast magnetization dynamics in CoDy alloy films. Investigating different chemical compositions and infrared pump fluences, we demonstrate the routine applicability of this technique. Probing in transmission the average magnetization dynamics of the entire film, our experimental findings indicate that the demagnetization time is independent of the specific infrared laser pump fluence. These results pave the way for the investigation of irreversible phenomena in a wide variety of scientific areas.

arXiv comment9 pages, 5 figures

References in corpus (10)

• Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization
• Nonequilibrium Magnetization Dynamics of Nickel
• Dispersive charge density wave excitations and temperature dependent commensuration in Bi2Sr2CaCu2O8+δ
• Speed limit of FePt spin dynamics on femtosecond timescales
• Separation of ultrafast spin currents and spin-flip scattering in Co/Cu(001) driven by femtosecond laser excitation via the complex MOKE
• Revealing the nature of the ultrafast magnetic phase transition in Ni by correlating extreme ultraviolet magneto-optic and photoemission spectroscopies
• Controlling the Polarity of the Transient Ferromagnetic-Like State in Ferrimagnets
• Unifying ultrafast demagnetization and intrinsic Gilbert damping in Co/Ni bilayers with electronic relaxation near the Fermi surface
• Structural dynamics during laser induced ultrafast demagnetization
• Element-resolved ultrafast demagnetization rates in ferrimagnetic CoDy

Cited by in corpus (6)

• Laser-induced ultrafast demagnetization and perpendicular magnetic anisotropy reduction in a Co${}_{88}$Tb${}_{12}$ thin film with stripe domains
• Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL
• Simultaneous two-color snapshot view on ultrafast charge and spin dynamics in a Fe-Cu-Ni tri-layer
• Spectroscopic probe of ultrafast magnetization dynamics in the extreme ultraviolet spectral range
• Time-Resolved XUV absorption spectroscopy and magnetic circular dichroism at the Ni $M_{2,3}$-edges
• Simultaneous mapping of the ultrafast time and fluence dependence of the laser-induced insulator-to-metal transition in magnetite