A5040701637- Iron oxide chemistry and applications
- Magnetic properties of thin films
- X-ray Spectroscopy and Fluorescence Analysis
- X-ray Diffraction in Crystallography
- Magnetic Properties and Synthesis of Ferrites
- Advanced Condensed Matter Physics
- Electron and X-Ray Spectroscopy Techniques
- Crystallography and Radiation Phenomena
- Multiferroics and related materials
- Advanced X-ray Imaging Techniques
- Magnetic and transport properties of perovskites and related materials
- Geomagnetism and Paleomagnetism Studies
- Nuclear Physics and Applications
- Organic and Molecular Conductors Research
- Magnetism in coordination complexes
- Characterization and Applications of Magnetic Nanoparticles
- Thermal Expansion and Ionic Conductivity
- Boron and Carbon Nanomaterials Research
- Particle Detector Development and Performance
- Nanocluster Synthesis and Applications
- Electronic and Structural Properties of Oxides
- Phase-change materials and chalcogenides
- Advanced Battery Materials and Technologies
- Radioactive element chemistry and processing
- Inorganic Chemistry and Materials
Institut de minéralogie, de physique des matériaux et de cosmochimie
2021-2024
Sorbonne Université
2021-2024
Centre National de la Recherche Scientifique
2021-2024
Sorbonne Paris Cité
2024
Utrecht University
2018-2023
Sorbonne University Abu Dhabi
2023
Institute for Magnetospheric Physics
2022
Diamond Light Source
2022
Institut de Recherche pour le Développement
2022
Cancer Genomics Centre
2019
This review provides an overview of the different methods and computer codes that are used to interpret 2p x-ray absorption spectra 3d transition metal ions. We first introduce basic parameters give used. start with semi-empirical multiplet compare available. A special chapter is devoted user friendly interfaces have been written on basis these codes. Next we discuss principle based band structure, including a Density Functional theory approaches. also first-principle from cluster...
Ag29 nanoclusters capped with lipoic acid (LA) can be doped Au. The clusters show enhanced stability and increased luminescence efficiency. We attribute the higher quantum yield to an increase in rate of radiative decay. With mass spectrometry, Au-doped were found consist predominantly Au1Ag28(LA)123-. characterized using X-ray absorption spectroscopy at Au L3-edge. Both extended fine structure (EXAFS) near edge (XANES) combination electronic calculations confirm that dopant is...
The fundamental optical excitations of correlated transition-metal compounds are typically identified with multielectronic transitions localized at the site, such as <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>d</a:mi><a:mi>d</a:mi></a:math> transitions. In this vein, intense interest has surrounded appearance sharp, below-band-gap transitions, i.e., excitons, within magnetic phase <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"...
Abstract Solid‐state electrolytes (SSEs) with high ionic conductivities are crucial for safer and high‐capacity batteries. Interface effects in nanocomposites of SSEs insulators can lead to profound increases conductivity. Understanding the composition interface is tuning conductivity composite solid electrolytes. Herein, X‐ray Raman Scattering (XRS) spectroscopy used first time unravel nature responsible enhancements complex hydride‐based (LiBH 4 , NaBH NaNH 2 ) oxides. XRS probe Li, Na, B...
Hematite, α-Fe2O3, is an important semiconductor for photoelectrochemical water splitting. Its low charge carrier mobility and the presence of midgap states provide favourable conditions electron-hole recombination, hence affecting semiconductor's efficiency. The nature excited state transport in hematite strongly debated. In order to further understand fundamental properties photoexcited state, we conducted femtosecond 2p (L3) X-ray absorption (XAS) 2p3d resonant inelastic scattering (RIXS)...
The VIolation of Pauli exclusion principle -2 experiment, or VIP-2 at the Laboratori Nazionali del Gran Sasso searches for X-rays from copper atomic transitions that are prohibited by principle. Candidate direct violation events come transition a 2p electron to ground state is already occupied two electrons. From first data taking campaign in 2016 we determined best upper limit [Formula: see text] probability such exists. Significant improvement control experimental systematics was also...
Understanding many-body physics of elementary excitations has advanced our control over material properties. Here, we study spin-flip in NiO using Ni L_{3}-edge resonant inelastic x-ray scattering (RIXS) and present a strikingly different energy behavior between single double excitations. Comparing results with single-site full-multiplet ligand field theory calculations find that the spectral weight double-magnon originates primarily from transition quadrupolar RIXS process within magnetic...
A photon carrying one unit of angular momentum can change the spin a magnetic system with (ΔMs = ±1) at most. This implies that two-photon scattering process manipulate maximum two units. Herein we describe triple-magnon excitation in α-Fe2O3, which contradicts this conventional wisdom only 1- and 2-magnon excitations are possible resonant inelastic X-ray experiment. We observe an exactly three times magnon energy, along additional four five suggesting quadruple quintuple-magnons as well....
Several definitions of the crystal field have been used over time and their variety has lead to many misunderstandings, in both theoretical experimental literature. Two categories can be mentioned, first being operators equivalents introduced by Stevens 1952 second crystal-field operators, different authors from 1962 expanded on Racah spherical tensors. This paper aims at providing some clarification this field. We make a review several expressions various references compute we describe...
We demonstrate the emergence and control of magnetic phases between magnetite (Fe3O4), a ferrimagnetic halfmetal, SrTiO3, transparent nonmagnetic insulator considered bedrock oxide-based electronics. The Verwey transition (TV) was detected to persist from bulk-like down ultrathin Fe3O4 films, decreasing 117 ± 4 K (38 nm) 25 (2 nm), respectively. Element-selective electronic properties films buried interfaces are studied by angle-dependent hard X-ray photoelectron spectroscopy circular...
Hematite (α-Fe2O3) is a photoelectrode for the water splitting process because of its relatively narrow bandgap and abundance in earth's crust. In this study, photoexcited state hematite thin film was investigated with femtosecond oxygen K-edge X-ray absorption spectroscopy (XAS) at PAL-XFEL order to follow dynamics states. The 200 fs decay time hole valence band observed via corresponding XAS feature.
A new methodology based on an adaptive grid algorithm followed by analysis of the ground state from fit parameters is presented to analyze and interpret experimental XAS L2,3-edge data. The fitting method tested first in a series multiplet calculations for d0-d7 systems which solution known. In most cases, able find solution, except mixed-spin Co2+Oh complex, where it instead revealed correlation between crystal field electron repulsion near spin-crossover transition points. Furthermore,...
The determination of the local orientation and magnitude magnetization in spin textures plays a pivotal role understanding harnessing magnetic properties for technological applications. Here, we show that by employing polarization dependence resonant inelastic X-ray scattering (RIXS), can directly probe ordering with chemical site selectivity. Applied on prototypical ferrimagnetic mixed-valence system, magnetite ([Fe3+]A[Fe3+,Fe2+]BO4), distinguish spin-flip excitations at A B...
The magnitude of the orbital magnetic moment and its role as a trigger Verwey transition in prototypical Mott insulator, magnetite, remain contentious. Using $1s2p$ resonant inelastic x-ray scattering angle distribution (RIXS-AD), we prove existence noncollinear ordering infer presence dynamical distortion creating polaronic precursor for metal to insulator transition. These conclusions are based on subtle angular shift RIXS-AD spectral intensity function field orientation. Theoretical...
We present 90 meV resolved Co $2p3d$ resonant inelastic x-ray scattering linear dichroism spectra of strained ${\mathrm{LaCoO}}_{3}$ films and a single crystal. A polarization-dependent low-energy excitation is observed at $\ensuremath{\sim}0.2\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ on the tensile-strained ${\mathrm{LaCoO}}_{3}/{\mathrm{SrTiO}}_{3}$ film, while it not in either bulk or compressive-strained ${\mathrm{LaCoO}}_{3}/{\mathrm{LaAlO}}_{3}$ film. Guided by cluster calculations, we...
Magnetite is one of the most fascinating materials exhibiting enigmatic first-order Verwey transition which conventionally manipulated through chemical doping. Here, we show that heating magnetite results in a spontaneous charge reordering and, consequently, hole self-doping effect at octahedral sublattice. Core-level x-ray spectroscopy measurements combined with theory uncovers there are three regimes map temperature dependence electrical conductivity and magnetism up to Curie temperature....
The orbital contribution to the magnetic moment of transition-metal ion in isostructural weak ferromagnets $A{\mathrm{CO}}_{3}$ ($A=$ Mn,Co,Ni) and ${\mathrm{FeBO}}_{3}$ was investigated by a combination first-principles calculations, nonresonant x-ray scattering, circular dichroism. A nontrivial evolution as function $3d$ orbitals filling is revealed, with particularly large value found Co member family. Here, coupling between lattice degrees freedom produced spin-orbit interaction results...
Abstract The systematic mineralogy of niobium (Nb) is complex, with more than one hundred species dominated by multicomponent oxides similar chemistry. determination Nb speciation in solids (i.e., the distribution between phases and crystal-chemical environment Nb) thus a challenge geological contexts. Here, we present first L2,3-edges X-ray absorption near-edge structure (XANES) measurements on various minerals synthetic relevance. interpretation XANES spectra light crystal-field theory...
Angle-dependent 2 p 3 d resonant inelastic X-ray scattering spectra of a LaCoO single crystal and 55 nm film on SrTiO substrate are presented. Theoretical calculation shows that, with ∼20 meV resolved Co (RIXS), the excited states isotropic 1 A g (O h ) ground state split by spin–orbit coupling, which can be distinguished via their angular dependence. However, strong self-absorption saturation effects distort limit observation small In contrast, RIXS less preserves dependence states.
The origin of the metal to insulator transition in ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ remains a challenge due complexity system: it is mixed valent, strongly correlated system where many interactions such as Jahn-Teller distortion, exchange, and phonons are very close energetics. A recent interpretation Verwey an ordering three-site magnetic polaron, trimeron, has been put forward. Here we investigate existence trimeron correlations high-temperature phase using high-resolution iron $2p3d$...
Copper tungstate (CuWO4) is an important semiconductor with a sophisticated and debatable electronic structure that has direct impact on its chemistry. Using the PAL-XFEL source, we study dynamics of photoexcited CuWO4. The Cu L3 X-ray absorption spectrum shifts to lower energy upon photoexcitation, which implies photoexcitation process from oxygen valence band tungsten conduction effectively increases charge density atoms. decay time this spectral change 400 fs indicating increased exists...
Magnetite (${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$) thin-films are among the most stimulating systems for electronic applications, in particular given that their electric and magnetic properties can be controlled by substrate strain. Here we investigate structure of a 38 nm ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}/{\mathrm{SrTiO}}_{3}\phantom{\rule{4pt}{0ex}}(001)$ thin-film unique set x-ray linear dichroism (XMLD) measurements. We show it is only possible to uncover orbital character Fe sites...
A procedure to build the optical conductivity tensor that describes full magneto-optical response of system from experimental measurements is presented. Applied Fe L 2,3 -edge a 38.85 nm 3 O 4 /SrTiO (001) thin-film, it shown computed polarization dependence using in excellent agreement with experimentally measured. Furthermore, magnetic field angular discussed set fundamental spectra expanded on spherical harmonics. It convergence this expansion depends details ground state question and...
The fundamental optical excitations of correlated transition-metal compounds are typically identified with multielectronic transitions localized at the site, such as $dd$ transitions. In this vein, intense interest has surrounded appearance sharp, below band-gap transitions, i.e. excitons, within magnetic phase Ni$^{2+}$ van der Waals magnets. interplay and charge-transfer insulating ground states in systems raises intriguing questions on roles long-range order metal-ligand charge transfer...