A5061068270- Ferroelectric and Piezoelectric Materials
- Acoustic Wave Resonator Technologies
- Advanced Condensed Matter Physics
- Particle accelerators and beam dynamics
- Multiferroics and related materials
- Gyrotron and Vacuum Electronics Research
- Physics of Superconductivity and Magnetism
- Microwave Dielectric Ceramics Synthesis
- Rare-earth and actinide compounds
- Solid-state spectroscopy and crystallography
- Magnetic and transport properties of perovskites and related materials
- Photorefractive and Nonlinear Optics
- Superconducting Materials and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Particle Accelerators and Free-Electron Lasers
- Electronic and Structural Properties of Oxides
- Superconductivity in MgB2 and Alloys
- Magnetic Properties and Synthesis of Ferrites
- High-pressure geophysics and materials
- Perovskite Materials and Applications
- Iron-based superconductors research
- X-ray Diffraction in Crystallography
- Advanced X-ray Imaging Techniques
- Laser Applications in Dentistry and Medicine
- Glass properties and applications
University of Balamand
2024
American University in Dubai
2024
European Synchrotron Radiation Facility
2013-2019
Beirut Arab University
2007-2018
Karlsruhe Institute of Technology
2017-2018
Université de Montpellier
2008-2015
Centre National de la Recherche Scientifique
2008-2015
Institut Charles Gerhardt Montpellier
2008-2015
Laboratoire Charles Coulomb
2011-2015
École Centrale Paris
2013-2014
An end-station for X-ray Raman scattering spectroscopy at beamline ID20 of the European Synchrotron Radiation Facility is described. This dedicated to study shallow core electronic excitations using non-resonant inelastic scattering. The spectrometer has 72 spherically bent analyzer crystals arranged in six modular groups 12 each a combined maximum flexibility and large solid angle detection. Each modules houses one pixelated area detector allowing based imaging efficient separation desired...
An end-station for resonant inelastic X-ray scattering and (resonant) emission spectroscopy at beamline ID20 of ESRF - The European Synchrotron is presented. spectrometer hosts five crystal analysers in Rowland geometry large solid angle collection mounted on a rotatable arm both the horizontal vertical planes. optimized high-energy-resolution applications, including partial fluorescence yield or detected absorption study elementary electronic excitations solids. In addition, it can be used...
We have studied the magnetic excitations of electron-doped Sr$_{2-x}$La$_x$IrO$_4$ ($0 \leq x 0.10$) using resonant inelastic x-ray scattering (RIXS) at Ir L$_3$-edge. The long range order is rapidly lost with increasing $x$, but two-dimensional short-range (SRO) and dispersive magnon nearly undiminished spectral weight persist well into metallic part phase diagram. magnons in SRO are heavily damped exhibit anisotropic softening. Their dispersions described by a pseudospin-1/2 Heisenberg...
In CaIrO3, electronic correlation, spin-orbit coupling, and tetragonal crystal field splitting are predicted to be of comparable strength. However, the nature its ground state is still an object debate, with contradictory experimental theoretical results. We probe CaIrO3 assess effective coupling at play in this system by means resonant inelastic x-ray scattering. conclude that insulating not a j(eff) = 1/2 iridate discuss consequences our finding interpretation previous experiments....
Sr${}_{3}$Ir${}_{2}$O${}_{7}$ is a member of the iridate Ruddlesden-Popper series Sr${}_{n+1}$Ir${}_{n}$O${}_{3n+1}$ with electronic properties that interpolate between insulating single-layer Sr${}_{2}$IrO${}_{4}$ ($n=1$) and metallic compound SrIrO${}_{3}$ ($n=\mathrm{\ensuremath{\infty}}$). Using resonant inelastic X-ray scattering (RIXS) experiments, authors reveal new magnetic mode propose model based on weakly coupled quantum dimers to describe observed excitation spectrum.
Hyper-Raman scattering experiments suggest that a splitting of the lowest F{1u}-symmetry mode PbMg{1/3}Nb{2/3}O{3} crystal occurs in wide temperature range around its Burns T{d}≈630 K. The upper-frequency component, earlier investigated by inelastic neutron above T{d}, appears to be underdamped even hundred degrees below T{d}. lower-frequency known T{d} from far-IR spectroscopy, actually becomes This suggests is "primary" polar soft PbMg{1/3}Nb{2/3}O{3}, responsible for Curie-Weiss behavior...
Topological insulators form a novel state of matter that provides new opportunities to create unique quantum phenomena. While the materials used so far are based on semiconductors, recent theoretical studies predict also strongly correlated systems can show non-trivial topological properties, thereby allowing even emergence surface phenomena not possible with band insulators. From practical point view, it is expected strong correlations will reduce disturbing impact defects or impurities,...
Significance The hidden order problem in URu 2 Si is an unanswered question the field of strongly correlated electron materials. Although it has been studied for several decades, there still no consensus about how this new phase forms. Understanding formation not only intellectual problem, will also advance concepts designing quantum materials with exotic properties. Many scenarios are based on assumption certain ground-state symmetries and present study addresses aspect. A spectroscopic...
Karlsruhe Institute of Technology (KIT) is doing research and development in the field megawatt-class radio frequency (RF) sources (gyrotrons) for Electron Cyclotron Resonance Heating (ECRH) systems International Thermonuclear Experimental Reactor (ITER) DEMOnstration Fusion Power Plant that will follow ITER. In focus verification European coaxial-cavity gyrotron technology which shall lead to gyrotrons operating at an RF output power significantly larger than 1 MW CW above 200 GHz. A major...
The fluctuations of electric polarization in a disordered ferroelectric substance, relaxor crystal PbMg_{1/3}Nb_{2/3}O_{3} (PMN), were studied using nonlinear inelastic light-scattering technique, hyper-Raman scattering, within 5-100 cm^{-1} spectral interval and broad temperature range from 20 to 900 K. split mode reveals local anisotropy up about 400 Spectral anomalies observed at higher temperatures are explained as due avoided crossing the single primary polar soft with...
Wavelength-dispersive high-resolution X-ray spectrometers often employ elastically bent crystals for the wavelength analysis. In a preceding paper [Honkanen et al. (2014). J. Synchrotron Rad. 21, 104-110] theory quantifying internal stress of macroscopically large spherically curved analyser crystal was presented. Here is applied to compensate corresponding decrease energy resolution. The technique demonstrated with Johann-type spectrometer using Si(660) in near-backscattering geometry,...
Non-resonant Raman spectroscopy in the hard X-ray regime has been used to explore electronic structure of first two members Ruddlesden-Popper series Sr$_{n+1}$Ir$_n$O$_{3n+1}$ iridates. By tuning photon energy transfer around 530 eV we have able oxygen K near edge with bulk sensitivity. The angular dependence spectra exploited assign features 528-535 range specific transitions involving Ir 5d orbitals. This allowed us extract reliable values for both t2g-eg splitting arising from cubic...
We present an in situ study of the thermal decomposition Mg(BH4)2 a hydrogen atmosphere up to 4 bar and 500 °C using X-ray Raman scattering spectroscopy at boron K-edge magnesium L2,3-edges. The combination fingerprinting analysis both edges yields detailed quantitative information on reaction products during decomposition, issue crucial importance determining whether can be used as next-generation storage material. This work reveals formation intermediate(s) 300 °C, accompanied by...
The high-pressure structure and dynamics of PbZr0.40Ti0.60O3 were investigated by means neutron diffraction, X-ray resonance Raman spectroscopy. complex (P4mm, Cm, Cc, F1, F1) phase transition sequence is characterized these techniques. On the basis results refinements, behavior spontaneous polarization, (Zr,Ti)O6 rotation angles, polarization angle are obtained. Moreover, spectra combined with previous data in literature provide evidence that pressure-induced to monoclinic Cm space group...
We characterize experimentally and theoretically the collective electronic excitations in two prototypical layered transition-metal dichalcogenides, ${\mathrm{NbSe}}_{2}$ ${\mathrm{Cu}}_{0.2}{\mathrm{NbS}}_{2}$. The energy- momentum-dependent dynamical structure factor was measured by inelastic x-ray scattering (IXS) spectroscopy simulated time-dependent density-functional theory. find good agreement between theory experiment, provided that Nb semicore states are taken into account together...
Nanoparticles of strontium titanate (SrTiO${}_{3}$) have been synthesized in the 15 nm to 1 \ensuremath{\mu}m size range and studied using a combination dielectric, Raman, x-ray, neutron measurements. When diminishing grain size, strong reduction dielectric permittivity, an enhancement (normally forbidden) Raman polar modes progressive decoupling (or nonlinear coupling) between antiferrodistortive (AFD) order parameter spontaneous strain, is observed. A qualitative explanation all these...
The electronic ferroelectric lutetium ferrite (${\mathrm{LuFe}}_{2}{\mathrm{O}}_{4}$) was studied by x-ray diffraction as a function of pressure. Pressure is shown to induce an irreversible rhombohedral orthorhombic transition leading supercell determined the combination electron and synchrotron diffraction. This new configuration proposed be charge ordered in agreement with results resistivity measurements.
A single crystal of the relaxor ${\text{PbMg}}_{1/3}{\text{Nb}}_{2/3}{\text{O}}_{3}$ is studied by hyper-Raman scattering. The relative scattering intensities obtained for band near $250\text{ }{\text{cm}}^{\ensuremath{-}1}$ in various polarization geometries are fully compatible with spectroscopy tensor ${F}_{2u}$ zone-center vibrational mode prototype $Pm\overline{3}m$ $({O}_{h}^{1})$ cubic perovskite structure. was investigated between room temperature and 775 K, thus covering range...
In spite of intensive experimental and theoretical studies, no model at the atomic scale has been proposed to explain large piezoelectric effect in ${\text{PbZr}}_{0.52}{\text{Ti}}_{0.48}{\text{O}}_{3}$ (PZT) compared low response simple end-member lead titanate ${\text{PbTiO}}_{3}$. X-ray absorption spectroscopy (XAS) appears as technique choice not only clarify role Zr, but also quantify Zr displacement through Ferroelectric-Paraelectric $(F\text{\ensuremath{-}}P)$ transition. We clearly...
Perovskite-type ferroelectric Pb(Zr${}_{1\ensuremath{-}x}$Ti${}_{x}$)O${}_{3}$ ($x$ $=$ 0.3; 0.4) compounds were investigated at high pressure by means of time-of-flight neutron powder and angle dispersive x-ray diffraction (NPD XRD) with special emphasis on the interactions between ${\ensuremath{\Gamma}}_{4}^{\ensuremath{-}}$ antiferrodistortive ${R}_{4}^{+}$ instabilities. A simple fast way for probing long-range level instability in perovskite is reported, which unlike Rietveld refinement...
Resonant inelastic x-ray scattering (RIXS) is an extremely valuable tool for the study of elementary, including magnetic, excitations in matter. Latest developments this technique mostly aimed at improving energy resolution and performing polarization analysis scattered radiation, with a great impact on interpretation applicability RIXS. Instead, article focuses sample environment presents setup high-pressure low-temperature RIXS measurements low-energy excitations. The feasibility these...
A well-known feature of CaFe$_{2}$As$_{2}$-based superconductors is the pressure-induced collapsed tetragonal phase that commonly ascribed to formation an interlayer As-As bond. Using detailed X-ray scattering and spectroscopy, we find Rh-doped Ca$_{0.8}$Sr$_{0.2}$Fe$_{2}$As$_{2}$ does not undergo a first-order transition local Fe moments persist despite bonds. Our density functional theory calculations reveal Fe-As bond geometry critical for stabilizing magnetism drop in $c$ lattice...