5,796 Works

Pressure driven phase transitions in the magnetically frustrated layered material, Ca2Mn3O8

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Frustration occurs in materials where antiferromagnetic (spin up and spin down pairs) are incomparible with the underlying crystal morphology, for example where the connectivity between magnetic ions has a triangular motif. In these magnetic materials the magnetically ordered state is often unconventional. Calcium manganese oxide, Ca2Mn3O8, exhibits managnese oxide layers seperated by calcium ions. Within the layers a complex "bow-tie" like connectivity of the maganese leads to a "two up two down" spin arrangement below...

Investigating the antiferromagnetic order in (001)pc SmNiO3/NdNiO3 superlattices

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Rare earth nickelates (RNO3, but La) display a metal to insulator transition (MIT) as the temperature is reduced together with an unusual antiferromagnetic (AFM) order described by the (1/4,1/4,1/4)pc-wavevector below the Néel transition (TNéel). By growing superlattices (SLs) that combine SmNiO3 (SNO) and NdNiO3 (NNO) layers two nickelates displaying different critical temperatures, we have found that TMI of the whole system is controlled by the thickness of the individual SNO and NNO layers. In...

Thermal expansion and magnetostriction in fayalite, Fe2SiO4

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Olivines - in particular the solid-solution between forsterite (Mg2SiO4) and fayalite (Fe2SiO4) - are important rock-forming minerals on Earth, also occurring in meteorites and interstellar dust. Olivines form the major component of Earth's upper mantle and the point at which their structure becomes unstable with respect to denser minerals marks the upper boundary of the transition zone between the upper and lower mantle. The thermal expansion of fayalite (Fe2SiO4) is unusual and not well understood...

Determination of the accurate crystal structure of Na2ZrO3 and its conversion to Na2CO3 upon CO2 uptake

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The aim of the proposal is to study the crystal structure of Na2ZrO3, which is one of the key solid-state materials for CO2 capture. Laboratory experiments have established a correlation between improved CO2 uptake and heating rates during synthesis. The experiment will enable characterisation of the structural differences between these samples, likely to be differing Na+ content, using neutron powder diffraction. This will involve room temperature data collected on a range of synthesised samples but...

Structural Investigations of Nickel-Substituted Bornite

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We wish to collect powder neutron diffraction data on modified bornites, Cu5Fe1-xNixS4 (0

Investigation of the magnetic structure of the charge transfer compound CuTCNQ

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Organic materials are playing an increasingly important role in electronic devices. An area of device technology where organics may make an impact is as memresistors, possibly in resistive random access memories . One material with potential is the charge transfer compound CuTCNQ (TCNQ = 7,7,8,8, -Tetracyanoquinodimethane), which exhibits electrical switching between low and high resistance states. One structural form of this material also exhibits magnetic order at low temperatures, the magnetism being associated with free...

Quantum critical dynamics in the presence of disorder

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Quantum phase transitions are abrupt qualitative changes of a system's groundstate occurring only at exactly zero temperature. Such critical points - although never reachable in their vicinity strongly impact many physical properties, even at comparably high temperatures. In fact, properties of many exotic materials are now linked to quantum phase transitions and these are studied intensely. Magnetic insulators make excellent model systems for such studies, as it is often possible to induce quantum phase...

Quantum spin-liquid state in a triangular lattice of S = 1/2 spin trimers in KBa3Ca4Cu3V7O28

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Geometrical frustration conspiring with quantum fluctuations in low-dimensional antiferromagnets has been demonstrated over the past years to lead to novel quantum states in condensed matter. Quantum spin liquids (QSL) on two-dimensional lattices are particularly intriguing, as they are extremely elusive and therefore poorly understood. Triangular lattice antiferromagnets are candidates for a QSL ground state if perturbations to the nearest-neighbour isotropic interactions are present. Here we focus on a novel triangular lattice of Cu2+ trimers in...

Low-temperature structural phase transitions in CuSeO4·5D2O and CuBeF4·5D2O

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The isostructural family of compounds that includes the familiar copper sulfate pentahydrate and the two less familiar title materials, has for decades been a model for studying a range of structural and magnetic phenomena. Our understanding of the magnetic transitions on cooling below 1 K have hitherto been based on an assumption that there is no preceding structural change, an assumption we now know to be false. We have shown that CuSO4.5D2O undergoes a loss...

Exchange kinetics of telechelic Cn-PEO-Cn micelles: effect of conformation and crystallinity

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The microscopic dynamics of associative polymers that self-assemble into micellar structures play a key role for their macroscopical properties, with important implications for their application, such as in drug delivery or viscosity modification. Here we study a well-defined model system consisting of hydrophilic poly(ethylene oxide) (PEO) which is end-capped with hydrophobic n-alkyl groups with various length (Cn-PEO-Cn). A previous systematic structural SAXS/SANS study has shown that, depending on the length of the alkane chain length,...

Magnetic ordering in the layered oxide arsenide Sr2Cr3As2O3

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This experiment will probe the evolution of magnetic ordering in Sr2Cr3As2O3, a compound containing Cr3+ moments in Cr2O square layers and Cr2+ moments in CrO2 layers. We will use temperature dependent measurements on WISH to probe the magnetic ordering on the two sublattices and whether there is any interaction between the two as well as any effects of the magnetic ordering on the crystal structure. We will compare the behaviour with that of related oxide...

Magnetic ordering in the layered oxide arsenide Sr2Cr3As2O3

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This experiment will probe the evolution of magnetic ordering in Sr2Cr3As2O3, a compound containing Cr3+ moments in Cr2O square layers and Cr2+ moments in CrO2 layers. We will use temperature dependent measurements on WISH to probe the magnetic ordering on the two sublattices and whether there is any interaction between the two as well as any effects of the magnetic ordering on the crystal structure. We will compare the behaviour with that of related oxide...

Ion and temperature effects on the self-assembly of short peptides - SANS studies

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In this work, we have selected a group of 5 short peptides I3GGHK, I4GGHK, I3GGGHK, I3GGHHK and I3KGGH to study how changes in peptide concentration, [Cu2+] and temperature affect their nanostructuring by SANS. Through extensive studies by AFM and TEM, we found that changes in GH position in the sequence can hugely affect nanostructures via altering peptide packing, layer thickness and twisting. These structural effects affect how molecules can align and form layers and extend...

Magnetic excitations in square lattice 2D Heisenberg Antiferromagnet Sr3Fe2O6.5

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Strontium iron oxides belonging to the RP series Srn+1FenO3n+1 (n = 1, 2, ..,1) may offer unique insights into the differences between the magnetic properties of the manganates,ruthenates, and ferrates. The present proposal on Sr3Fe2O6.5 is motivated by our recent observations that there is a change in crystal structure from tetragonal (for Sr3Fe2O7) to orthorhombic ( for Sr3Fe2O6.5), where the 4-fold symmetry is lost. A preliminary refinement suggests that in the magnetic structure moments lie...

Magnetic excitations in square lattice 2D Heisenberg Antiferromagnet Sr3Fe2O6.5

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Strontium iron oxides belonging to the RP series Srn+1FenO3n+1 (n = 1, 2, ..,1) may offer unique insights into the differences between the magnetic properties of the manganates,ruthenates, and ferrates. The present proposal on Sr3Fe2O6.5 is motivated by our recent observations that there is a change in crystal structure from tetragonal (for Sr3Fe2O7) to orthorhombic ( for Sr3Fe2O6.5), where the 4-fold symmetry is lost. A preliminary refinement suggests that in the magnetic structure moments lie...

Measurement of muonic X-rays using a segmented calorimeter towards an observation of parity violation in muonic atoms

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The proposed experiment aims to establish a detector system for a measurement of parity-violating effect in muonic atoms. A measurement of parity violation in atoms is a precision test of the standard model of particle physics via the determination of the Weinberg angle at low-energy scale. Furthermore, atomic parity violation in muonic atoms provides a unique opportunity to search for an unknown particle coupling to the muon. Parity violation in muonic atoms can be observed...

Excited/Ground State of Kekulé di-radical Material Bisphenalenyl

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Kekulé di-radical (KDR) with two radical centers of independent spins has a low-spin ground state (singlet S0 with antiparallel spins), and interestingly high-spin triplets (T1) can be thermally activated and populated at high temperature to advance the room-temperature spin-active properties of KDR materials. Hence, it is important to microscopically study the electronic structures of S0 and T1 of KDRs. We plan to use photo-pump muon-probe muSR to learn photo induced effect on muSR spectra at...

structure of surfactant-free microemulsion as the L-L equilibirum line is approached

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A surfactant-free microemulsion is ternary system consisting of two completely miscible molecular liquids and a third one that is only highly soluble in or miscible with one of these two other liquids. These solutions are excellent solubilizers and candidates in terms of formulation for green chemistry. The microemulsions are stabilized thanks to the repulsion mechanism induced by the hydration force at the interface and no addition electrical charges are required. The system of interest is...

Small Angle Neutron Scattering Measurement of Precipitation in 17-4PH Martensitic Stainless Steel

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This work aims to understand the precipitation behaviour of nanoscale precipitates in 17-4PH grade martensitic stainless steel as a function of aging time and temperature.17-4PH is used in safety critical components in the chemical, oil and gas and nuclear industry but has driven concerns over the long term stability of the precipitate population. We propose to investigate the evolution of these precipitates using small angle neutron scattering (SANS) on a series of thermally aged samples....

Neutron diffraction study of A-site deficient hydrated Perovskites

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Transition metal ions can be easily introduced in the B-site of perovskites with general formula ABO3 and exsolved on their surfaces upon reduction, to enhance the catalytic properties in energy applications such as solid oxide cells. Based on the stoichiometries we explored so far, we have good experimental evidence to believe that Ni2+ ions could also be substituted on the A-site of hydrated CaTiO3 and then exsolved upon reduction. Formation of unusual non-stoichiometries with a...

Intergranular strain formation in Nickel based superalloys close to the yield point.

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Nickel based superalloys retain high strength up to high temperatures and are therefore often used in gas turbines. Here, hardening mechanisms and their respective supersessions are investigated in order to better predict phenomena like dynamic strain ageing, creep and yield point shape. Neutron diffraction for intergranular strain determination at the onset of plastic deformation in the Nickel based superalloy Haynes 282 displays strong, unexpected features, which are assumed to be associated with segregations of substitutional...

Intergranular strain formation in Nickel based superalloys close to the yield point.

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Nickel based superalloys retain high strength up to high temperatures and are therefore often used in gas turbines. Here, hardening mechanisms and their respective supersessions are investigated in order to better predict phenomena like dynamic strain ageing, creep and yield point shape. Neutron diffraction for intergranular strain determination at the onset of plastic deformation in the Nickel based superalloy Haynes 282 displays strong, unexpected features, which are assumed to be associated with segregations of substitutional...

Investigation of membrane polymer complex using SANS

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The interaction between lipid vesicles and macromolecules, like polymers is of intense importance from both theoretical and practical point of view. On one hand lipid vesicles can successfully mimic cell membrane on the other hand only on understanding the effect of polymer-lipid interaction one can control the mechanism and degree of polymer encapsulation in passive (no active chemical trigger) in a drug delivery (cargo). But such fine-tuning is only possible on changing the hydrophobic: hydrophilic...

Structural evidence from SANS on self-assembly of antimicrobial lipopeptides and their interactions with small unilamellar vesicles

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Previous studies have demonstrated that the de novo designed antimicrobial lipopeptides can self-assemble to beta-sheet nanofibers, but can transform to alpha-helical monomers once interacting with the anionic bacterial membranes. Following the above work, we propose to investigate the structural evidence of the self-assembly of lipopeptides by using small angel neutron scattering (SANS) to characterise the nanofibers before and after interactions with small unilamellar vesicles (SUVs). This work will provide valuable molecular insight of modes of...

Evaluation of defects in TlBr single crystal using energy resolved neutron imaging

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Our research group at Nagoya University pursues a programme of radiation detector development for a range of applications. The purpose of this experiment is to evaluate the defects in TlBr single crystals, which are used for semiconductor radiation detectors. TlBr has recently been developed as an alternative to the high purity germanium (HPGe) detector. It can be operated at room temperature and shows excellent energy resolution of less than 1%. The current key issue is...

Registration Year

  • 2019
    5,796

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  • Dataset
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Affiliations

  • University of Edinburgh
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