5,796 Works

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...

Looking for the elusive alpha tin phase

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The characteristics of metal alloys have always been considered crucial for the sound quality of organ pipes. Tin-rich materials were studied for conservation issues, like the so-called tin pest -a consequence of a tin crystal structure change. Tin pest is indeed an allotropic transformation of tin, from beta-phase (tetragonal structure) to alpha-phase (diamond-cubic structure). This phase transformation, spontaneous below 13.2 °C, is strongly accelerated by lower temperatures. Recently, we studied a wide set of tin-based...

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...

Oxidation of gram-negative cell-wall proxy with OH radicals - kinetics and mechanism for water industry II

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Hydroxyl radicals may be used as disinfection agent in the advanced oxidation processes or tertiary treatment of waste and occasionally drinking water. We very recently oxidised a gram negative bacterial cell wall proxy at the liquid-solid interface with aqueous hydroxyl radical, the experiment (RB1820244) was a complete success and is being written up as a letter for publication. Our previous exploratory work, demonstrated the polysaccharides are an effective layer to resist oxidative attack, but did...

muSR Study on the Electron Transfer Mechanism of a Blue Copper Protein, Pseudoazurin

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In order to establish the method to apply polarized muon for study of biological functions and life sciences, we need to perform systematic study to know the behavior of muon in bio-molecules and know what information can be extracted from the implantation of muon in different macromolecules. Here we propose to study the electron transfer mechanism in blue Copper protein - Pseudoazurin(PAz) using muon. The PAz has single-copper ion binding site that serves as an...

QENS study of Proton Diffusion in Functional Metal-Organic Frameworks

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Complex proton conductors based upon metal-organic frameworks (MOFs) have attracted increasing interests for applications in fuel cells. We have developed new proton conductors based on stable and functionalised MOFs [MFM-300 (Cr) and MFM-300 (Cr)-SO3H]. Importantly, MFM-300(Cr)-SO3H exhibited remarkable proton conductivity (>10-2 S/cm at 25 oC under 98%RH), which is comparable with the current leading commercial material based upon Nifion polymers (10-1 S/cm at 60 to 80 oC under 98%RH). We request 7 days on IRIS...

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...

Structural Investigations of Nickel-Substituted Bornite

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

Controlling the interaction of hemicellulose (galactoglucomannan, GGM) with cellulose by means of enzyme modification

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Softwood hemicellulose (galactoglucomannan, GGM) is one of the major plant polysaccharides found in cell walls after cellulose. It makes up to 25% of the wood in Sweden, however, currently most of it is obtained as a by-product of several industrial processes and discarded in waste-stream. The aim of the project is to develop sustainable processes to biocatalytically modify GGM structure in order to transform it to a versatile and excellent renewable resource for novel high-performance...

Cross sections of some efficient slow-neutron reflectors

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The proposal seeks to investigate the reflection capacity of two systems that are candidates for use in the design of cold neutron sources. These are carbon nanodiamonds and magnesium hydride. The first shows a strong Small Angle Neutron Scattering component in its cross section, while the second has scattering distributions closer to the isotropy. The comparison between forward and backward scattering signals will serve to evaluate such properties. In addition, the transmission measured with the...

A detailed study of magnetic diffuse scattering in a low-dimension ferromagnet CePdSb

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We have carried out detailed investigations on the ferromagnetic (FM) Kondo lattice CePdSb, in polycrystal as well as single crystal form (TC=17.5K) using magnetization, neutron diffraction, inelastic neutron scattering and heat capacity. This has turned out to be an extraordinary compound, which exhibits pronounced anomaly at 10 K, well below TC=17.5K in the heat capacity and small-angle neutron scattering (SANS) and very weak anomaly at TC. Surprisingly, the correlation lengths in the ab-plane as well...

Inelastic neutron scattering studies on novel frustrated antiferromagnets Li3Mg2MO6 (M = Ru, Os)

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A newly discovered novel frustrated antiferromagnets Li3Mg2MO6 (M = Ru, Os) constitutes edge-sharing triangles of M4+ ions (S = 3/2) linked by corner-sharing in the ab-plane. The M spins interact with each other via four different antiferromagnetic exchange interactions, J1, J2, J3 and J4. Despite the considerable geometrical frustration, Li3Mg2MO6 exhibits an antiferromagnetic long-range order at TN = 18 K for M = Ru and TN = 8 K for M = Os. Heat capacity...

Measuring the spin-wave spectrum of the room temperature metal-organic spintronic material V[TCNE]2

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Organic-based materials have found applications in a wide variety of devices, including light emitting diodes, photovoltaics, and field effect transistors. These take advantage of the low cost, chemical tunability, and mechanical flexibility of this class of materials. Vanadium tetracyanoethylene (V[TCNE]x~2) exhibits ferimagnetic order well above room temperature (TN > 600K), and an ultra-narrow ferromagnetic resonance (FMR) linewidth , making it a competetive alternative to best-in-class inorganic materials. Despite its popularity, little is known about the...

Low-temperature structures of Prussian blue analogues for electrochemical applications

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We propose a low-temperature diffraction study at POLARIS of Prussian blue analogues (PBAs) of general formula NaxMM'(CN)6, where 1 < x 2. These systems currently attract intense research interest due to their potential applications as electrodes in sodium ion batteries. In order to fully understand the electrochemical processes, accurate structural models are vital. At present, the most favourable position of Na in the framework is debated and we believe that this diffraction study will be...

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  • 2019
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