A5018479500- Nuclear Materials and Properties
- Radioactive element chemistry and processing
- Nuclear reactor physics and engineering
- Rare-earth and actinide compounds
- Fusion materials and technologies
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Nuclear Physics and Applications
- Nuclear materials and radiation effects
- Magnetic and transport properties of perovskites and related materials
- Magnetic properties of thin films
- Iron-based superconductors research
- High Temperature Alloys and Creep
- Multiferroics and related materials
- High-pressure geophysics and materials
- Electronic and Structural Properties of Oxides
- Hydrogen embrittlement and corrosion behaviors in metals
- Quantum and electron transport phenomena
- Theoretical and Computational Physics
- Thermodynamic and Structural Properties of Metals and Alloys
- Radioactive contamination and transfer
- Nuclear and radioactivity studies
- Advanced Power Generation Technologies
- Microstructure and mechanical properties
- Machine Learning in Materials Science
University of Bristol
2016-2025
Interface (United Kingdom)
2013-2022
Cabot (United States)
2018-2019
University of Ulster
2012-2015
Royal Victoria Hospital
2012-2015
University College London
2004-2014
London Centre for Nanotechnology
2012-2014
European Synchrotron Radiation Facility
2008-2013
The magnetic structure and electronic groundstate of the layered perovskite Ba2IrO4 have been investigated using x-ray resonant scattering (XRMS). Our results are compared with those for Sr2IrO4, which we provide supplementary data on its structure. We find that dominant, long-range antiferromagnetic order is remarkably similar in two compounds, Ba2IrO4, deduced from an investigation XRMS $L_3/L_2$ intensity ratio, consistent a $J_{eff}=1/2$ description. robustness these key properties to...
Sr2IrO4 is a prototype of the class Mott insulators in strong spin–orbit interaction (SOI) limit described by Jeff = 1/2 ground state. In Sr2IrO4, SOI predicted to manifest itself locking canting magnetic moments correlated rotation 11.8(1)° oxygen octahedra that characterizes its distorted layered perovskite structure. Using x-ray resonant scattering at Ir L3 edge we have measured accurately intensities Bragg peaks arising from different components From careful comparison integrated due...
We investigate the high-energy magnetic excitation spectrum of high-T(c) cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi-2212) using Cu L(3) edge resonant inelastic x-ray scattering. Broad, dispersive excitations are observed, with a zone boundary energy ∼ 300 meV and weak dependence on doping. These strikingly similar to bosons proposed explain "kink" observed in photoemission. A phenomenological calculation spin response, based parametrization angle-resolved photoemission spectroscopy...
We report on a detailed x-ray resonant scattering study of the bilayer iridate compound ${\mathrm{Sr}}_{3}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ at Ir ${L}_{2}$ and ${L}_{3}$ edges. Resonant edge has been used to determine that is long-range ordered antiferromagnet below ${T}_{N}\ensuremath{\approx}230\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ with an ordering wave vector $\mathbf{q}=(\frac{1}{2},\frac{1}{2},0)$. The energy resonance was found be factor $\ensuremath{\sim}30$ times larger than edge....
XPS determination of the oxygen coefficient kO = 2 + x and ionic (U4+, U5+, U6+) composition oxides UO2+x formed on surfaces differently oriented (hkl) planes thin UO2 films LSAT (Al10La3O51Sr14Ta7) YSZ (yttria-stabilized zirconia) substrates was performed. The U 4f O 1s core–electron peak intensities as well 5f relative intensity before after 129Xe23+ 238U31+ irradiations were employed. It found that presence uranium dioxide film in air results formation oxide surface with mean coefficients...
The magnetic critical scattering in ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ has been characterized using x-ray resonant (XRMS) both below and above the three-dimensional antiferromagnetic ordering temperature ${T}_{\text{N}}$. order parameter exponent ${T}_{\text{N}}$ is found to be $\ensuremath{\beta}=0.195(4)$, range of two-dimensional (2D) $XY{h}_{4}$ universality class. Over an extended ${T}_{\text{N}}$, amplitude correlation length intrinsic fluctuations are well described by 2D...
A (111) air-exposed surface of UO2 thin film (150 nm) on YSZ (yttria-stabilized zirconia) before and after the Ar+ etching subsequent in situ annealing spectrometer analytic chamber was studied by XPS technique. The U 5f, 4f O 1s electron peak intensities were employed for determining oxygen coefficient kO = 2 + x a UO2+x oxide surface. It found that initial (several had 2.20. 20 s led to formation UO2.12, whose composition does not depend significantly time (up 180 s). at temperatures...
The magnetic correlations within the cuprates have undergone intense scrutiny as part of efforts to understand high temperature superconductivity. We explore evolution along nodal direction Brillouin zone in La2-xSrxCuO4, spanning doping phase diagram from anti-ferromagnetic Mott insulator at x = 0 metallic 0.26. Magnetic excitations this are found be systematically softened and broadened with doping, a higher rate than anti-nodal direction. This phenomenology is discussed terms nature...
Philippe Marcus opened a general discussion of the paper by Roger Newman: Should passive film not be significantly involved in pit initiation (as you suggest), how would explain that time to is very much dependent on nature film? Ne
X-ray diffraction has been used to probe the radiolytic corrosion of uranium dioxide. Single crystal thin films UO(2) were exposed an intense beam at a synchrotron source in presence water, order simultaneously provide radiation fields required split water into highly oxidising products, and structure composition layer, morphology UO(2)/water interface. By modeling electron density, surface roughness layer thickness, we have able reproduce observed reflectivity profiles detect changes oxide...
A neptunium analogue of the LaFeAsO tetragonal layered compound has been synthesized and characterized by a variety experimental techniques. The occurrence long-range magnetic order below critical temperature T_N = 57 K is suggested anomalies in temperature-dependent susceptibility, electrical resistivity, Hall coefficient, specific heat curves. Below T_N, powder neutron diffraction measurements reveal an antiferromagnetic structure Np sublattice, with ordered moment 1.70(0.07) \mu_B aligned...
We have conducted a series of scattering experiments at the uranium M4 absorption edge on low-symmetry compounds (U2N3 and U3O8) produced as epitaxial films. At weak forbidden reflections, we find resonant signal, independent temperature, with an energy dependence resembling imaginary part factor. Theory, using FDMNES code, shows that these results can be reliably reproduced assuming they originate from aspherical 5f electron charge distributions around U nucleus. Such effects arise...
Thin films (250--4500 \AA{}) of epitaxial UO${}_{2}$ were produced by reactive sputtering on two different substrate materials: LaAlO${}_{3}$ and CaF${}_{2}$. Using the large enhancement present with resonant x-ray scattering using photons at uranium $M$${}_{4}$ absorption edge, antiferromagnetic (AF) order was found in all films. The ordering temperature $T$${}_{N}$ is same as bulk, but show second-order (continuous) transitions contrast to first-order bulk transition. For...
X-ray magnetic circular dichroism (XMCD) measurements were performed at the U ${M}_{4,5}$ edges and Fe $K$ edge on well-defined uranium/iron multilayers with different compositions. The have layer thicknesses in range $9--40\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ for uranium $9--34\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ iron. At both $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ room temperature, layers are magnetically polarized all of studied. To deduce moment from XMCD results requires...
The actinide cubic Laves compounds NpAl${}_{2}$, NpOs${}_{2}$, NpFe${}_{2}$, and PuFe${}_{2}$ have been examined by x-ray magnetic circular dichroism (XMCD) at the ${M}_{4,5}$ absorption edges Os ${L}_{2,3}$ edges. They interesting feature that $An\ensuremath{-}An$ spacing is close to so-called Hill limit so substantial hybridization between 5$f$ states on neighboring atoms expected occur. XMCD experiments performed of Np Pu allow us determine spectroscopic branching ratio, which gives...
This report presents azimuthal dependent and polarization x-ray resonant magnetic scattering at the Ir L3 edge for bilayered iridate compound Sr3Ir2O7. The two wave vectors, , result in domains of symmetry-related G-type antiferromagnetic structures, denoted A B, respectively. These are approximately 0.02 mm2 independent thermal history. An understanding this key aspect magnetism is necessary an overall picture behaviour compound. dependence reflections, relating to both wavevectors, show...
Epitaxial thin films of ThO2 and (UxTh1−x)O2 mixed oxides (MOX) have been synthesised by DC magnetron sputtering. The samples were characterised using x-ray diffraction spectroscopic ellipsometry. Three epitaxial different crystallographic orientations confirmed analysis. are [1 1 1], 0] [0 0 1] oriented, with lattice parameters determined to be 5.714 ± 0.001 Å, 5.707 Å 5.624 respectively. Four oriented fabricated, across 0≤x≤1, all found a unique specular direction. obey Vegard's law,...
Abstract Although the principal physical behaviour of a material is inherently connected to its fundamental crystal structure, behaviours observed in real-world are often driven by microstructure, which for many polycrystalline materials, equates size and shape constituent grains. Here we highlight cutting edge synthesis route controlled engineering grain structures thin films simplification associated 3-dimensional problems less complex 2D ones. This has been applied actinide ceramic,...