A5024204702- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Multiferroics and related materials
- Nuclear Physics and Applications
- Advanced NMR Techniques and Applications
- Ferroelectric and Piezoelectric Materials
- Inorganic Chemistry and Materials
- Magnetic properties of thin films
- Corporate Taxation and Avoidance
- Intellectual Capital and Performance Analysis
- Atomic and Subatomic Physics Research
- Inorganic Fluorides and Related Compounds
- Solid-state spectroscopy and crystallography
- High-pressure geophysics and materials
- 2D Materials and Applications
- Crystal Structures and Properties
- Magneto-Optical Properties and Applications
- Zeolite Catalysis and Synthesis
- Catalysis and Oxidation Reactions
- Acoustic Wave Resonator Technologies
- Catalytic Processes in Materials Science
- Organic and Molecular Conductors Research
Rutherford Appleton Laboratory
2015-2024
ISIS Neutron and Muon Source
2023
China Spallation Neutron Source
2023
State Key Laboratory of Surface Physics
2022
Fudan University
2022
Research Complex at Harwell
2020
Science and Technology Facilities Council
2018-2019
University of Oxford
2006-2010
The HORACE suite of programs has been developed to work with large multiple-measurement data sets collected from time-of-flight neutron spectrometers equipped arrays position-sensitive detectors. software allows exploratory studies the four dimensions reciprocal space and excitation energy be undertaken, enabling multi-dimensional subsets visualized, algebraically manipulated, models for scattering simulated or fitted data. is designed an extensible framework, thus allowing user-customized...
Neutron inelastic scattering has been used to measure the magnetic excitations in powdered ${\mathrm{NiPS}}_{3}$, a quasi-two-dimensional antiferromagnet with spin $S=1$ on honeycomb lattice. The spectra show clear, dispersive magnons $\ensuremath{\sim}7$ meV gap at Brillouin zone center. data were fitted using Heisenberg Hamiltonian single-ion anisotropy assuming no exchange between planes. Magnetic interactions up third intraplanar nearest neighbor required. fits robustly that...
We have performed powder inelastic neutron scattering measurements on the unconventional superconductor $\beta$-FeSe ($T_{\rm c} \simeq 8\,\mathrm{K}$). The spectra reveal highly dispersive paramagnetic fluctuations emerging from square-lattice wave vector $(\pi,0)$ extending beyond 80 meV in energy. Measurements as a function of temperature at an energy $\sim 13\,\mathrm{meV}$ did not show any variation $T_{\rm c}$ to $104\,\mathrm{K}$. results that FeSe is close instability towards...
We use neutron scattering to show that ferromagnetic (FM) phase transition in the two-dimensional (2D) honeycomb lattice ${\mathrm{CrI}}_{3}$ is a weakly first order and controlled by spin-orbit coupling (SOC) induced magnetic anisotropy, instead of exchange as conventional ferromagnet. With increasing temperature, magnitude seen spin gap at Brillouin zone center, decreases power law fashion vanishes ${T}_{C}$, while in-plane $c$-axis spin-wave stiffnesses associated with couplings remain...
Neutron spectroscopy measurements have been performed on single crystals of the antiferromagnetic van der Waals compound NiPS$_3$. Linear spin wave theory using a Heisenberg Hamiltonian with single-ion anisotropies has applied to determine magnetic exchange parameters and nature anisotropy. The analysis reveals that NiPS$_3$ is less two-dimensional than its sister compounds, relatively large ferromagnetic $J^{\prime} = -0.3$ meV between layered \emph{ab} planes. In-plane interactions up...
We report neutron-scattering measurements of cooperative spin excitations in antiferromagnetically ordered ${\text{BaFe}}_{2}{\text{As}}_{2}$, the parent phase an iron pnictide superconductor. The data extend up to $\ensuremath{\sim}100\text{ }\text{meV}$ and show that excitation spectrum is sharp highly dispersive. By fitting a linear spin-wave model we estimate magnon bandwidth be region 0.17 eV. large characteristic spin-fluctuation energy suggests magnetism could play role formation...
We report neutron inelastic-scattering measurements on the stoichiometric iron-based superconductor LiFeAs. find evidence for (i) magnetic scattering consistent with strong antiferromagnetic fluctuations and (ii) an increase in intensity superconducting state at low energies, similar to resonant excitation observed other superconductors. The results do not support a recent theoretical prediction of spin-triplet $p$-wave superconductivity LiFeAs but instead suggest that mechanism is
We report inelastic neutron scattering measurements of the magnetic excitations in SrFe2As2, parent a family iron-based superconductors. The data extend throughout Brillouin zone and up to energies ~260meV. An analysis with local-moment J_1-J2 model implies very different in-plane nearest-neighbor exchange parameters along $a$ $b$ directions, both orthorhombic tetragonal phases. However, spectrum calculated from J1-J2 deviates significantly our data. show that qualitative features cannot be...
The magnetic insulator Yttrium Iron Garnet can be grown with exceptional quality, has a ferrimagnetic transition temperature of nearly 600 K, and is used in microwave spintronic devices that operate at room temperature. most accurate prior measurements the magnon spectrum date back 40 years, but cover only 3 lowest energy modes out 20 distinct branches. Here we have time-of-flight inelastic neutron scattering to measure full throughout Brillouin zone. We find existing model excitation...
The parent compound of high-[Formula: see text] superconducting cuprates is a unique Mott insulator consisting layers spin-[Formula: ions forming square lattice and with record high in-plane antiferromagnetic coupling. Compounds similar characteristics have long been searched for without success. Here, we use combination experimental theoretical tools to show that commercial [Formula: an excellent cuprate analog remarkably electronic parameters but larger buckling planes. Two-magnon Raman...
The MAPS direct geometry time-of-flight chopper spectrometer at the ISIS pulsed neutron and muon source has been in operation since 1999, its novel use of a large array position-sensitive detectors paved way for later generations spectrometers around world. Almost two decades experience user operations on MAPS, together with lessons learned from new generation instruments, led to decision perform three parallel upgrades instrument. These were replace primary beamline collimation supermirror...
Abstract Stacking two-dimensional (2D) van der Waals (vdW) materials in a layered bulk structure provides an appealing platform for the emergence of exotic physical properties. As vdW crystal with exceptional plasticity, InSe offers opportunity to explore various effects arising from coupling its peculiar mechanical behaviors and other Here, we employ neutron scattering techniques investigate correlations plastic interlayer slip, lattice anharmonicity, thermal transport crystals. Not only...
We report on an extensive investigation of the multiferroic compound $\mathrm{Tb}\mathrm{Mn}{\mathrm{O}}_{3}$ using x-ray scattering techniques. Nonresonant magnetic (NRXMS) was used to characterize domain population single crystal in our experiments. This revealed that dominant is overwhelmingly $A$ type. The temperature dependence intensity and wave vector associated with incommensurate order found be good agreement neutron data. X-ray resonant experiments were performed vicinity Mn $K$ Tb...
Using polarized neutron scattering we establish that the magnetic order in ${\mathrm{La}}_{1.48}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_{0.12}{\mathrm{CuO}}_{4}$ is either (i) one dimensionally modulated and collinear, consistent with stripe model or (ii) two a novel noncollinear structure. The measurements rule out number of alternative models characterized by 2D electronic 1D helical spin order. low-energy excitations are found to be primarily transversely relative ordered state, conventional waves.
We report neutron inelastic scattering measurements on the normal and superconducting states of single-crystalline Cs0.8Fe1.9Se2. Consistent with previous Rb(x)Fe(2-y)Se2, we observe two distinct spin excitation signals: (i) spin-wave excitations characteristic block antiferromagnetic order found in insulating A(x)Fe(2-y)Se2 compounds, (ii) a resonance-like magnetic peak localized energy at 11 meV an in-plane wave vector (0.25, 0.5). The resonance increases below Tc = 27 K, has similar...
Neutron spectroscopy is used to investigate the magnetic fluctuations in Fe_{1+x}Te - a parent compound of chalcogenide superconductors. Incommensurate "stripe-like" excitations soften with increased interstitial iron concentration. The energy crossover from incommensurate stripy defines an apparent hour-glass dispersion. Application sum rules neutron scattering find that integrated intensity inconsistent S=1 Fe^{2+} ground state and significantly less than S=2 predicted weak crystal field...
We use inelastic neutron scattering to study energy and wave vector dependence of spin fluctuations in ${\mathrm{SrCo}}_{2}{\mathrm{As}}_{2}$, derived from ${\mathrm{SrFe}}_{2\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{As}}_{2}$ iron pnictide superconductors. Our data reveal the coexistence antiferromagnetic (AF) ferromagnetic (FM) at vectors ${\mathbf{Q}}_{\mathrm{AF}}=(1,0)$ ${\mathbf{Q}}_{\mathrm{FM}}=(0,0)/(2,0)$, respectively. By comparing results with those dynamic mean field theory...
CoO has an odd number of electrons in its unit cell, and therefore is expected to be metallic. Yet, strongly insulating owing significant electronic correlations, thus classifying it as a Mott insulator. We investigate the magnetic fluctuations using neutron spectroscopy. The strong spatially far-reaching exchange constants reported [Sarte et al. Phys. Rev. B 98 024415 (2018)], combined with single-ion spin-orbit coupling similar magnitude [Cowley 88, 205117 (2013)] results mixing between...
Refinements to established sample handling issues connected with the acquisition of inelastic neutron scattering (INS) spectra heterogeneous catalyst samples are described. This involves modification a reactor and improvements gas apparatus. The latter includes provision laboratory space ventilation facilities that suited increasingly wide range catalytic being examined. INS measurements for CO hydrogenation over an iron-based Fischer-Tropsch recorded using MARI spectrometer presented...
CaFe_{2}O_{4} is a S=5/2 anisotropic antiferromagnet based upon zig-zag chains having two competing magnetic structures, denoted as the A (↑↑↓↓) and B (↑↓↑↓) phases, which differ by c-axis stacking of ferromagnetic stripes. We apply neutron scattering to demonstrate that phase order parameters result in antiphase boundaries along c freeze on time scale ∼1 ns at onset 200 K. Using high resolution spectroscopy, we find quantized spin wave levels measure 9 such excitations localized regions...
Layered molecular-intercalated iron selenides (FeSe) show great promise as a class of high-${T}_{\mathrm{c}}$ unconventional superconductors, with ${T}_{\mathrm{c}}$ high 45 K reported so far. The FeSe layers in these materials also structural and electronic similarities to monolayer on SrTiO${}_{3}$, where values up 65 have been observed. Information the superconducting properties may provide vital insight into mechanism high-temperature superconductivity iron-based compounds. One property...
Abstract The NaZn 13 type itinerant magnet LaFe 13− x Si has seen considerable interest due to its unique combination of large magnetocaloric effect and low hysteresis. Here, this alloy with a magnetometry, bespoke microcalorimetry, inelastic neutron scattering is investigated. Inelastic reveals the presence broad quasielastic that persists across magnetic transition, which attributed spin fluctuations. In addition, peak observed at Q = 0.52 Å −1 for 1.2 exists only in paramagnetic state...