A5071815422- Magnetic properties of thin films
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced X-ray Imaging Techniques
- High-pressure geophysics and materials
- Physics of Superconductivity and Magnetism
- Electron and X-Ray Spectroscopy Techniques
- Advanced Condensed Matter Physics
- X-ray Diffraction in Crystallography
- Magnetic and transport properties of perovskites and related materials
- Crystallography and Radiation Phenomena
- Magnetic Properties and Applications
- Rare-earth and actinide compounds
- Zeolite Catalysis and Synthesis
- Advanced Chemical Physics Studies
- Characterization and Applications of Magnetic Nanoparticles
- Magneto-Optical Properties and Applications
- Magnetic Properties of Alloys
- Nuclear Physics and Applications
- Advanced Electron Microscopy Techniques and Applications
- Theoretical and Computational Physics
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Iron oxide chemistry and applications
- Boron and Carbon Nanomaterials Research
- Atomic and Subatomic Physics Research
SLAC National Accelerator Laboratory
2014-2023
Linac Coherent Light Source
2020
Stanford University
2016
Menlo School
2009-2015
Stanford Synchrotron Radiation Lightsource
1991-2015
Yonsei University
2007-2015
Brookhaven National Laboratory
2001-2010
National Synchrotron Light Source II
1991-2010
Argonne National Laboratory
1999-2009
Lawrence Berkeley National Laboratory
2009
Compressed under ambient temperature, graphite undergoes a transition at approximately 17 gigapascals. The near K-edge spectroscopy of carbon using synchrotron x-ray inelastic scattering reveals that half the pi-bonds between layers convert to sigma-bonds, whereas other remain as in high-pressure form. diffraction pattern form is consistent with distorted structure which bridging atoms pair and nonbridging unpaired pi-bonds. superhard, capable indenting cubic-diamond single crystals.
Charge density wave (CDW) correlations have recently been shown to universally exist in cuprate superconductors. However, their nature at high fields inferred from nuclear magnetic resonance is distinct that measured by x-ray scattering zero and low fields. Here we combine a pulsed magnet with an free electron laser characterize the CDW YBa2Cu3O6.67 via up 28 Tesla. While zero-field order, which develops below T ~ 150 K, essentially two-dimensional, lower temperature beyond 15 Tesla, another...
Specular reflectivity of p-polarized light near the iron ${\mathit{L}}_{\mathrm{II}}$ and ${\mathit{L}}_{\mathrm{III}}$ absorption edges was measured from a single-crystal film with an external magnetic field perpendicular to scattering plane. Large changes in were observed upon reversal direction field. We attribute this resonant magnetization-sensitive effect interference between nonmagnetic contribution scattering. Similar effects can be expected other ferromagnetic ferrimagnetic systems.
Efficient encapsulation of functionalized spherical nanoparticles by viral protein cages was found to occur even if the nanoparticle is larger than inner cavity native capsid. This result raises intriguing possibility reprogramming self-assembly structural proteins. The iron oxide nanotemplates used in this work are superparamagnetic, with a blocking temperature about 250 K, making these virus-like particles interesting for applications such as magnetic resonance imaging and biomagnetic...
The existence of charge density wave (CDW) correlations in cuprate superconductors has now been established. However, the nature ground state order remained uncertain because disorder and presence superconductivity typically limit CDW correlation lengths to a dozen unit cells or less. Here we explore YBa2Cu3Ox (YBCO) ortho-II ortho-VIII crystals, which belong cleanest available family, at magnetic fields excess resistive upper critical field (Hc2) where is heavily suppressed. We find an...
Interaction of light with matter is paramount importance in nature. The most fundamental property a material relation to its oscillator strength distribution, i.e., how strongly it absorbs as function wavelength. Once the distribution determined precisely for wide enough energy range, optical constants such absorbance and reflectance well number other properties material, some which are seemingly unrelated photoabsorption, can be deduced. Most important all fact that interaction fast charged...
We report evidence for a preserved magnetic state in FeO up to 143 GPa at room temperature using high-resolution x-ray emission spectroscopy. This observation is based on the spectral line shape of Fe $K\ensuremath{\beta}$ line. Up highest pressure, remains insulator. Combining our results with previous M\"ossbauer data, we present new phase diagram FeO. Features like closed-loop $P\ensuremath{-}T$ antiferromagnetic domain confirm that high-pressure investigations can reveal physical...
We report the observation of pressure-induced high-spin to low-spin transition in FeS using new high-pressure synchrotron x-ray emission spectroscopy techniques. The is evidenced by disappearance low-energy satellite Fe $K\ensuremath{\beta}$ spectrum FeS. Moreover, phase reversible and closely related structural from a manganese phosphidelike monoclinic phase. study opens opportunities for investigating electronic properties materials under pressure.
We report inelastic x-ray scattering studies of charge excitations in insulating ${\mathrm{Nd}}_{2}{\mathrm{CuO}}_{4}$ as a function incident photon energy. An excitation $\ensuremath{\sim}6\mathrm{eV}$ is observed when the energy tuned through Cu $K$ edge. This interpreted resonantly enhanced scattering. Numerical calculations identify 6 eV feature charge-transfer to antibonding state and suggest that nonlocal effects play role determining shape resonance.
Dichroic interference effects were observed in circularly polarized soft-x-ray reflectivity at the Co ${\mathit{L}}_{2,3}$ edges of a magnetic multilayer. The data show maximum asymmetry ratio 80%, greater than degree circular polarization incident light, changeover dichroic characteristics with increasing grazing angle, and an inverted pattern angular dependence ratio. These observations are explained successfully by classical electromagnetic model calculation which includes complete state...
A method to measure spin-dependent x-ray-absorption spectra that does not require long-range magnetic order is presented. It based on the spin dependence of emission spectrum. Using a high-resolution spectrometer separate and select different spin-polarized final states in K\ensuremath{\beta} fluorescence spectrum MnO ${\mathrm{MnF}}_{2}$, absorption vicinity Mn K edge were measured. Since this uses direction local moment as reference it can be applied paramagnetic antiferromagnetic systems...
Resonant soft X-ray scattering (RSXS) is a powerful technique for probing both spatial and electronic structures within solid-state systems.We present newly developed RSXS capability at beamline 13-3 of the Stanford Synchrotron Radiation Lightsource (SSRL), designed to enhance materials science research. This advanced setup achieves base sample temperature as low 9.8 K combined with extensive angular motions (azimuthal \phi flipping \chi), enables comprehensive exploration reciprocal space....
The weak ${2p}^{5}{4f}^{n+1}$ quadrupolar excitation is separated from the intense ${2p}^{5}{5d}^{1}$ white line at gadolinium ${L}_{\mathrm{III}}$ absorption edge in ${\mathrm{Gd}}_{3}{\mathrm{Ga}}_{5}{O}_{12}$ by resonant inelastic x-ray scattering. This separation obtained monitoring intensity of ${3d}^{9}{4f}^{n+1}{5d}^{0}$ and ${3d}^{9}{4f}^{n}{5d}^{1}$ multiplet families, which are resonantly enhanced intermediate energies, respectively. dipolar excitations detected spite Gd $2p$...
The near K-edge structure of oxygen in liquid water and ices III, II, IX at 0.25 GPa several low temperatures down to 4 K has been studied using inelastic x-ray scattering 9884.7 eV with a total energy resolution 305 175 meV. A marked decrease the preedge intensity from phase ice III II is attributed ordering hydrogen bonds proton-ordered lattice latter phases. Density functional theory calculations including influence Madelung potential crystal correctly account for remaining feature....
Iron is one of the most studied chemical elements due to its sociotechnological and planetary importance; hence, understanding structural transition dynamics vital interest. By combining a short pulse optical laser an ultrashort free electron pulse, we have observed subnanosecond iron from high-quality x-ray diffraction data measured at 50-ps intervals up 2500 ps. We unequivocally identify three-wave structure during initial compression two-wave decaying shock, involving all known types (α-,...
An energy loss feature with transfer close to the anion-to-cation charge-transfer of NiO is observed in inelastic-x-ray-scattering spectrum as incident x-ray tuned through Ni K absorption edge NiO. The inelastic-scattering cross section shows large resonant enhancement and strong dependence. These observations are interpreted using a configuration-interaction cluster model \textcopyright{} 1996 American Physical Society.
Using micro-fabrication techniques, we have manufactured a single element kinoform lens in single-crystal silicon with an elliptical profile for 12.398 keV (1A) x-rays. By fabricating that is optimized at fixed wavelengths, absorption the material can be significantly reduced by removing 2_ phase-shifting regions. This permits short focal length devices to fabricated small radii of curvatures apex. feature allows one obtain high demagnification finite synchrotron electron source size. The...
Resonant inelastic x-ray scattering spectra are recorded at the ${L}_{3}$ absorption edge of rare-earth ions in ${R}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$. In all cases, weak resonances observed energies below dipolar white line resonance, originating from $2p\ensuremath{\rightarrow}4f$ quadrupolar excitations. Their energy position is excellent agreement with that preedge features magnetic circular dichroism (XMCD) same samples. Our results therefore evidence systematic appearance excitation...
We report the observation of resonant x-ray magnetic scattering in vicinity Ni K edge antiferromagnet NiO. An approximately twofold increase is observed as incident photon energy tuned through a pre-edge feature absorption spectrum, associated with quadrupolar (1s\ensuremath{\rightarrow}3d) transitions. No enhancement at dipolar (1s\ensuremath{\rightarrow}4p) maximum. The amplitude estimated to be \ensuremath{\sim}0.${01\mathrm{r}}_{0}$.
We demonstrate an element-specific measurement of magnetization precession in a metallic ferromagnetic alloy, separating $\mathrm{Ni}$ and $\mathrm{Fe}$ moment motion ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$. Pump-probe x-ray magnetic circular dichroism, synchronized with short field pulses, is used to measure free oscillations up $2.6\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ elemental specificity rotational resolution $<2\ifmmode^\circ\else\textdegree\fi{}$. Magnetic moments residing on sites...
We demonstrate a layer- and time-resolved measurement of ferromagnetic resonance (FMR) in ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}∕\mathrm{Cu}∕{\mathrm{Co}}_{93}{\mathrm{Zr}}_{7}$ trilayer structure. Time-resolved x-ray magnetic circular dichroism has been developed transmission, with resonant field excitation at FMR frequency $2.3\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$. Small-angle (to 0.2\ifmmode^\circ\else\textdegree\fi{}), time-domain magnetization precession could be observed directly,...
The detailing of the intermolecular interactions in dense solid oxygen is essential for an understanding rich polymorphism and remarkable properties this element at high pressure. Synchrotron inelastic x-ray scattering measurements K-edge excitations to 38 GPa reveal changes electronic structure bonding on compression molecular solid. show that O 2 molecules interact predominantly through half-filled 1π g * orbital <10 GPa. Enhanced develop because increasing overlap low-pressure phases,...