A5005364885- Magnetic properties of thin films
- Advanced X-ray Imaging Techniques
- Laser-Matter Interactions and Applications
- Advanced Electron Microscopy Techniques and Applications
- Laser-Plasma Interactions and Diagnostics
- Magneto-Optical Properties and Applications
- Magnetic Properties and Applications
- Particle Accelerators and Free-Electron Lasers
- Magnetic and transport properties of perovskites and related materials
- Crystallography and Radiation Phenomena
- ZnO doping and properties
- Advanced Fiber Laser Technologies
- Spectroscopy and Quantum Chemical Studies
- Quantum and electron transport phenomena
- X-ray Spectroscopy and Fluorescence Analysis
- Electronic and Structural Properties of Oxides
- Atomic and Molecular Physics
- Gyrotron and Vacuum Electronics Research
- Magnetic Properties of Alloys
- Physics of Superconductivity and Magnetism
- Photonic Crystal and Fiber Optics
- Advanced Chemical Physics Studies
- Advancements in Photolithography Techniques
- Particle accelerators and beam dynamics
- Terahertz technology and applications
Sorbonne Université
2016-2025
Centre National de la Recherche Scientifique
2015-2024
Laboratoire de Chimie Physique - Matière et Rayonnement
2014-2024
Deutsches Elektronen-Synchrotron DESY
2021
Paul Scherrer Institute
2020
Elettra-Sincrotrone Trieste S.C.p.A.
2014-2020
AREA Science Park
2020
University of Nova Gorica
2020
Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy
2017-2020
Université Paris-Saclay
2016-2018
During ultrafast demagnetization of a magnetically ordered solid, angular momentum has to be transferred between the spins, electrons, and phonons in system on femto- picosecond timescales. Although intrinsic spin-transfer mechanisms are intensely debated, additional extrinsic arising due nanoscale heterogeneity have only recently entered discussion. Here we use femtosecond X-ray pulses from free-electron laser study thin film samples with magnetic domain patterns. We observe an...
We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and dynamics can be outrun pulses shorter than 80 fs in investigated fluence regime, no permanent aftereffects samples are observed below a 25 mJ/cm2. Employing resonant spatially muliplexed holography results low imaging threshold 5 Our open new ways to combine ultrafast laser spectroscopy sequential snapshot on single sample, generating movie excited...
Recent advances in high-harmonic generation gave rise to soft X-ray pulses with higher intensity, shorter duration and photon energy. One of the remaining shortages this source is its restriction linear polarization, since yield elliptically polarized high harmonics has been low so far. We here show how limitation overcome by using a cross-polarized two-colour laser field. With simple technique, we reach degrees ellipticity (up 75%) efficiencies similar classically generated linearly...
Ultrashort, coherent x-ray pulses of a free-electron laser are used to holographically image the magnetization dynamics within magnetic domain pattern after creation localized excitation via an optical standing wave. We observe spatially confined reduction couple hundred femtoseconds followed by its slower recovery. Additionally, experimental results show evidence spatial evolution magnetization, which we attribute ultrafast transport nonequilibrium spin-polarized electrons for early times...
We report the generation of circularly polarized high order harmonics in extreme ultraviolet range (18-27 nm) from a linearly infrared laser (40 fs, 0.25 TW) focused into neon filled gas cell. To polarize initially we have implemented four-reflector phase-shifter. Fully radiation has been obtained with an efficiency few percents, thus being significantly more efficient than currently demonstrated direct elliptically harmonics. This demonstration opens up new experimental capabilities based...
The FERMI facility in Trieste, Italy, is ideal for generating and measuring light characterized by tunable polarization states the vacuum ultraviolet spectral range. New results reveal a high degree of (>0.9) over 26--55 nanometers.
Abstract Does the excitation of ultrafast magnetization require direct interaction between photons optical pump pulse and magnetic layer? Here, we demonstrate unambiguously that this is not case. For have studied dynamics a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon with intense femtosecond-short IR laser pulse, film exhibits classical demagnetization phenomenon although only negligible number penetrate In comparison uncapped reference film, initial...
The authors report ferromagnetism at room temperature in Co doped CeO2−δ thin films grown by pulsed laser deposition on SrTiO3 and Si substrates. On ceria is epitaxied displays a high crystalline quality. the are textured with dominant orientation. While little affected amounts of structural defects, it depends sensitively oxygen pressure during growth annealing. This indicates that vacancies could be involved magnetic coupling between ions. Furthermore, epilayers display large anisotropy an...
We report the first experimental demonstration of a laser-driven circularly polarized soft-x-ray laser chain. It has been achieved by seeding 32.8 nm Kr ix plasma amplifier with high-order harmonic beam, which using four-reflector polarizer. Our measurements testify that amplified radiation maintains initial polarization seed pulse in good agreement our Maxwell-Bloch modeling. The resulting fully circular beam exhibits Gaussian profile and yields about 1010 photons per shot, fulfilling...
Recently several techniques demonstrated the production of elliptically polarized high harmonics. One these consists interaction in a noble gas two-color laser beams having orthogonal linear polarizations. Here we present theoretical explanation such result observed Lambert et al. [Nat. Commun. 6, 6167 (2015)]. Numerical calculations based on nonperturbative light-atom theory reproduce well experimental data. The degree polarization is analyzed for different harmonic orders and found to be...
Understanding the loss of magnetic order and microscopic mechanisms involved in laser induced magnetization dynamics is one most challenging topics today's magnetism research. While scattering between spins, phonons, magnons electrons have been proposed as sources for dissipation spin angular momentum, ultrafast dependent transport hot has pointed out a potential candidate to explain demagnetization without resorting any channel. Here we use time resolved magneto-optical Kerr measurements...
We present results of single-shot resonant magnetic scattering experiments Co/Pt multilayer systems using 100 fs long ultraintense pulses from an extreme ultraviolet (XUV) free-electron laser. An x-ray-induced breakdown the channel during pulse duration is observed at fluences 5 J/cm(2). Simultaneously, speckle contrast high-fluence pattern significantly reduced. performed simulations nonequilibrium evolution system XUV duration. find that electronic state sample strongly perturbed first few...
We present an element specific and spatially resolved view of magnetic domains in Co/Pt heterostructures the extreme ultraviolet spectral range. Resonant small-angle scattering coherent imaging with Fourier-transform holography reveal nanoscale domain networks via dichroism Co at M2,3 edges as well strong dichroic signals O2,3 N6,7 Pt. demonstrate for first time simultaneous, two-color a free-electron laser facility paving way direct real space access to ultrafast magnetization dynamics...
Development of ultrafast table-top x-ray sources that can map various spin, orbital, and electronic configurations reordering processes on their natural time length scales is an essential topic for modern condensed matter physics as well science. In this work, we demonstrate spatiotemporally resolved resonant magnetic scattering (XRMS) to probe the inner-shell 4d electrons a rare-earth (RE) composite ferrimagnetic system using bright <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Numerous methods have been developed to retrieve the full temporal properties of ultrafast infrared laser pulses, and are presently implemented on facilities all around world. We present here a technique, for XUV domain, suitable characterize any femtosecond picosecond pulse, that can be routinely produced high variety existing sources harmonics, free electron lasers, plasma-based lasers. Especially, versatility is such no limitation property potential source exists. Our technique relies...
The structural and magnetic properties of cobalt nanowires embedded in epitaxial ${\text{CeO}}_{2}$ layers are investigated. Combining electron microscopy with x-ray absorption spectroscopy, we show that polycrystalline metallic Co formed during the growth. These oriented average along growth axis a misalignment distribution, have predominant hcp structure narrow distribution diameters. Their overall dominated by shape effects an easy mean direction wires axis. reversal mechanism is studied...
Ultrashort optical pulses can trigger a variety of non-equilibrium processes in magnetic thin films affecting electrons and spins on femtosecond timescales. In order to probe the charge degrees freedom simultaneously, we developed an x-ray streaking technique that has advantage providing jitter-free picture absorption cross section changes. this paper, present experiment based approach which performed using five photon probing energies at Ni $M_{2,3}$-edges. This allowed us retrieve circular...
We use time-resolved x-ray resonant magnetic scattering (tr-XRMS) at the Co M$_{2,3}$- and Tb O$_1$-edges to study ultrafast demagnetization in an amorphous Co$_{88}$Tb$_{12}$ alloy with stripe domains. Combining femtosecond temporal nanometer spatial resolution of our experiment, we demonstrate that equilibrium spin texture thin film remains unaltered by optical pump-pulse on ultrashort timescales ($<$1 ps). However, after $\simeq$ 4 ps, observe onset a significant domain wall broadening,...
The ferromagnetic response from Co-doped CeO2 epilayers is shown to be linked the formation of Co metallic nanowires (diameters in 3–7 nm range) within oxide matrix. These results (i) illustrate key role shape anisotropy inclusions diluted magnetic oxides (DMO), (ii) stress importance monitor out-of-plane DMO, and (iii) suggest that some dilute systems previously thought intrinsic ferromagnet may reexamined.
Ultrafast demagnetization, a phenomenon of utmost interest in the context optical control magnetically recorded data, has been extensively studied variety different materials. However, only limited number studies have investigated impact pump laser wavelength on process, and within narrow spectral range. Performing resonant scattering experiment at cobalt ${M}_{2,3}$ edges, using extreme ultraviolet radiation photons from high harmonic source, we ultrafast demagnetization dynamics Co/Pt...
Laser-driven non-local electron dynamics in ultrathin magnetic samples on a sub-10 nm length scale is key process ultrafast magnetism. However, the experimental access has been challenging due to nanoscopic and femtosecond nature of such transport processes. Here, we present scattering-based experiment relying laser-induced electro- magneto-optical grating Co/Pd ferromagnetic multilayer as new technique investigate magnetization nanometer timescales. We induce spatially modulated excitation...
The mechanism underlying femtosecond laser pulse induced ultrafast magnetization dynamics remains elusive despite two decades of intense research on this phenomenon. Most experiments focused so far characterizing and charge carrier dynamics, while first direct measurements structural during demagnetization were reported only very recently. We here present our investigation the infrared process in a thin Ni film, which characterizes simultaneously dynamics. This is achieved by employing time...
We systematically study the fluence dependence of resonant scattering cross-section from magnetic domains in Co/Pd-based multilayers. Samples are probed with single extreme ultraviolet (XUV) pulses femtosecond duration tuned to Co M_{3,2} absorption resonances using FERMI@Elettra free-electron laser. report quantitative data over 3 orders magnitude fluence, covering 16 mJ/cm^{2}/pulse 10 000 pulse lengths 70 fs and 120 fs. A progressive quenching diffraction is observed. Compression same...