cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.5286/isis.e.rb1510152
title: Superconducting gap structure of the cage compound Sc5Rh6Sn18: A muon spin relaxation study

description: Recently we have investigated the superconducting state of the caged type compound R5Rh6Sn18 (R = Lu and Y) by using magnetization, heat capacity, and muon-spin relaxation or rotation measurements. Our zero-field µSR measurements clearly reveal the spontaneous appearance of an internal magnetic field below the transition temperature, which indicates that the superconducting state in these materials is characterized by the broken time-reversal symmetry. Further the analysis of temperature dependence of the magnetic penetration depth for Lu5Rh6Sn18 measured using the transverse field MUSR measurements suggest an isotropic s-wave character for the superconducting gap. We want to study zero-field (ZF), transverse field (TF) and longitudinal field (LF) to investigate microscopic superconducting properties of Sc5Rh6Sn18 using MUSR spectrometer.
DOI: 10.5286/isis.e.rb1510242
title: Coexistence of superconductivity and magnetism in the half-Heusler compound ErPdBi

description: This half-Heusler compound is also a semi-metal, with a low carrier density and non-trivial topological features. The crystal structure is also non-centrosymmetric, which is interesting from a superconductivity point of view, as one expects an admixture of conventional spin singlet and unconventional spin triplet pairing states. Additionally, this system develops a magnetically ordered phase in the region of superconductivity. It is not known if the ordering is anti-ferromagnetic, or a more exotic spin spiral state. It is also unknown to what extent the magnetism plays a role with the superconductivity. In this proposal we seek to solve the nature of the magnetic order, and investigate thoroughly its role with the superconductivity.
DOI: 10.5286/isis.e.rb1510306
title: Spin dynamics in the Tomonaga-Luttinger liquid system SrCo2V2O8

description: SrCo2V2O8 is believed to belong to the same rare universality class as Tomonaga-Luttinger liquids, which may be descrived by the 1D XXZ model.  In SrCo2V2O8, this is accomplished by means of antiferromagnetic (AFM) screw chains of Co2+ running up the c-axis.  These chains are weakly coupled, giving a rather anisotropic ordering the basal plane.  By tuning T and B, a very rich phase diagram is observed: a quantum critical order-to-disorder transition is seen with magnetic field perpendicular or parallel to c.  Later, an incommenusrate longitudinal spin density wave (LSDW) is speculated to exist near the Neel phase at higher magnetic fields at low temperatures.  Here, we propose to study the spin dynamics near the boundary of the proposed LSDW state and the standard AFM phase.
DOI: 10.5286/isis.e.rb1510381
title: Spin liquid properties of the S=1/2 triangular lattice system Li2ZnMo3O8

description: Thermal, magnetic, neutron and muSR measurements all point towards a gapless or almost gapless spin liquid ground state for the triangular lattice spin system of S=1/2 Mo3 clusters in the compound Li2ZnMo3O8. It is suggested that 2/3 of the spins form a honeycomb valence bond solid (VBS) below 100 K with a finite spin gap, leaving the remaining 1/3 of the spins to form a gapless triangular lattice spin liquid with an enlarged lattice constant and weakened coupling via the VBS sites. New muon measurements will explore the boundary between spin liquid and magnetic phases and will be used to extract critical parameters to test against existing models. A search will also be made for the signature of 2D diffusive motion of spin excitations, a feature that was seen in several other triangular lattice spin liquids previously studied with muons, giving further information about the criticality.
DOI: 10.5286/isis.e.rb1510385
title: Temperature and environment dependence of the isotope effect in muonated radicals

description: We plan to measure the hyperfine constants for both the muon and the equivalent hydrogen atom in a small muonated radical using time-differential ALC. We will follow this as a function of temperature to observe the isotope effect on the vibrational states. Measurements will be made in solutions giving different environments (aqueous - polar and hydrocarbon - non polar). The work will lead on to locating such molecules in practical multi-phase systems such as surfactants, giving partition fractions and exchange or diffusion rates.
DOI: 10.5286/isis.e.rb1510387
title: Probing the [FeFe]-hydrogenase using muon spectroscopy

description: During our previous experiment on HiFi (RB1320541) we measured the ALC spectrum of the Fe2(µ-pdt)(CO)4(PMe3)2 model hydrogenase complex over multiple temperatures. The spectra were characterised by two broad features which we were able to assign to a bridging and a terminally muoniated species, with the former being the dominant. In the current application our goals are threefold: 1) we would like to extend the field region of the ALC spectrum in the solid state to hunt for the Δ1 resonances predicted by our DFT calculations, 2) continue  our investigation of addition sites and dynamics in solution where isotropy will remove Δ1 resonances (which could be masking Δ0 resonances in the solid state), 3) measure muonium addition rates over a number of dilute concentrations using ALC line the broadening technique.
DOI: 10.5286/isis.e.rb1520003
title: The ferroelectric phase transition in Dion-Jacobson layered perovskites

description: Several distinct families of layered perovskites have been shown experimentally to display ferroelectricity. The most recent of these is the Dion-Jacobson (DJ) family, typified by compositions such as CsBiNb2O7, which has now been shown to be ferroelectric with a TC of ~ 1033 C. Simultaneously, theoretical studies have suggested that ferroelectricity in the DJ family arises from a 'trilinear coupling', whereby two non-polar lattice modes interact in such a way to cooperate with a third, polar mode. Both these studies were prompted by our own earlier work, which predicted ferroelectricity in CsBiNb2O7 based on a crystallographic study at ISIS. Unfortunately, our earlier VT study only extended to 900 C; with the benefit of hindsight(!) it is clear that a further study is prompted in order to clarify the exact nature of the ferro-paraelectric transition in this and related compounds.
DOI: 10.5286/isis.e.rb1520312
title: Structural studies of methyl stearate

description: In order to tackle emissions targets for CO2, there is increasing pressure to replace fossil fuels with renewable fuels. Biodiesel is one such renewable transportation fuel that comprises long-chain saturated fatty acid methyl esters such as methyl stearate.  Although biodiesel has many advantages compared to conventional diesel, it suffers from poor performance at low temperatures on account of crystallisation in fuel lines and in high-pressure injectors. We are currently investigating the crystallisation of biodiesel under low-temperature and high-pressure conditions, and are using methyl stearate as a model compound.  The aim of the proposed experiment is to use high-resolution neutron powder diffraction to obtain the crystal structure of methyl stearate. This will contribute to the development of crystal-habit modifiers that prevent blockage of fuel lines in cold conditions.
DOI: 10.5286/isis.e.rb1610011
title: X-N Charge Density and Isotope Effects in the Low-Barrier N-HN Hydrogen Bonds in H3Co(CN)6 and D3Co(CN)6

description: Our goal with this project is to gain insight into the bonding mechanisms of low barrier N-HN hydrogen bonds and how increased thermal energy changes the charge density distribution of these strong hydrogen bonds. Furthermore we wish to study how the isotope effect manifests itself in the charge density.To study the charge density one need highly accurate and high resolution X-ray diffraction data. However, in this case due to the weak X-ray scattering power of hydrogen/deuterium, neutron data is needed to describe the position and thermal motion of H/D. Both X-ray and neutron diffraction data is combined in one refinement, a so-called X-N charge density refinement. We already have collected high resolution and high quality X-ray data and therefore, we ask for beam time to complete the neutron diffraction experiments.
DOI: 10.5286/isis.e.rb1610032
title: Magnetism in the martensitic phase of Ni2Mn1.4In0.6 and Ni1.8Co0.2Mn1.4In0.6 magnetic shape memory alloys.

description: We propose to solve the long standing controversy regarding the magnetic state of off-stoichiometric Heusler alloys Ni2Mn1.4In0.6 and Ni1.8Co0.2Mn1.4In0.6 at temperatures below the magneto-structural transition and establish whether the materials are compensated ferrimagnets with zero net moment or paramagnets.
DOI: 10.5286/isis.e.rb1610063
title: Magnetic order in Metamagnetic Shape Memory Alloys: a muon study

description: Metamagnetic Shape Memory Alloys (MMSMAS) undergo a martensitic transformation which is accompanied with a large drop in magnetization on cooling, making the low temperature phase (martensite) either weakly magnetic or non magnetic at all, in stark contrast and contrary to the conventional behaviour of magnetic materials. Such behaviour enables the achievement of the reverse transformation into austenite by application of a moderate magnetic field. The ferrimagnetism of the austenitic phase is well documented. However, the magnetic character of the martensitic phase remains controversial and different behaviours, such as a spin glass phase, antiferromagnetic or just a paramagnetic phase have been suggested. We propose to carry out a muon spin rotation and relaxation study on the Ni42Co8Mn39Sn11 MMSM alloy to discriminate the presence of spin-glass or weak antiferromagnetic phases.
DOI: 10.5286/isis.e.rb1610438
title: Variable Temperature Neutron Diffraction Studies of Thermal Battery Cathode Materials

description: Thermal batteries find use in applications such as emergency power systems and ejector seats in aircraft.  As a result, systems need to be highly reliable.  This requires a detailed knowledge of the structure and the stability of the individual components of the battery at operating temperatures (typically 400-500 °C).  We are currently undertaking a project which involves the synthesis, properties and characterisation of materials which may be used as cathodes in thermal batteries.  We have recently gained good electrochemical performances with materials which have not been characterised tested as cathodes.  The aim of this experiment would be to gain accurate structural models for the cathode materials at elevated temperature and understand how the structure evolves with temperature.
DOI: 10.5286/isis.e.rb1610461
title: Structural studies of the KSbO3-type osmates Sr6Os6O19 and Bi3Os3O11

description: Osmium-based oxides show a wide range of interesting properties due to the variety of oxidation states osmium can adopt combined with 5d electrons displaying strong spin-orbit coupling. We plan to investigate the ambient- and low-temperature structures of Sr6Os6O19 and Bi3Os3O11 to understand the electronic structure and magnetism in these compounds. Both compounds have cubic KSbO3-type structures with osmium-osmium bonds and both show anomalies in magnetic susceptibility at low temperature. Special attention will be given to these osmium-osmium bonds in our analysis as well as the oxygen coordination of the Os ions, both of which are crucial for understanding the magnetism and electronic properties of these materials.
DOI: 10.5286/isis.e.rb1610472
title: Investigating the role of Oxygen in the delafossite-spinel transformations in CuFe1-xCrO2

description: CuFe1-xCrO2 has potential applications as an SOFC cathode material.  It exhibits and interesting transformation on oxidation.  This is a follow on from our recent HRPD experiment which has yielded interesting results.
DOI: 10.5286/isis.e.rb1620057
title: Probing the Magnetism and Suspected Quantum Fluctuations in Green Dioptase

description: It has been suggested that within green dipotase there the magnetism is dominated by quantum flucuations but evidence for this is not definitive. This means that in this naturally occuring mineral there is still debate regarding the magnetism at low temepratures, is it well ordered or are there dominent flucutations that disturb this order. This material is made up of Cu(II) chains that are antiferromagnetically coupled and the interaction between these chains are ferromagnetic, each Cu(II) ions also only has 3 nearest neighbours, which is a small coordination number. Muon spectroscopy may help provide answers as to what's going on, especially given that the muon is both a local and bulk probe that is extremely sensitive to magentic flucutations.
DOI: 10.5286/isis.e.rb1620456
title: Investigating Superconductivity and charge density wave in 2H-PdxTaSe2

description: The role and interplay of the different charge degrees of freedom remain a central issue in many unconventional superconductors. PdxTaSe2 series is an ideal system to study such effect where commensurate charge density wave state destabilized rapidly upon systematic intercalation of Pd ions and quantum critical phase transition occurs at x ~ 0.09 - 0.10. Moreover, Tc also shows a dramatic enhancement at the transition. It has been proposed that the increase of the density of states and effective electron-phonon coupling in the vicinity of CDW quantum phase transition is the key to such large enhancement of Tc in PdxTaSe2. Here we propose to study the evolution of the density of states, gap symmetry and the coupling strength of the PdxTaSe2 series (x = 0.5, 0.75, 0.9, 1.0, 1.25, 1.5) using muSR technique. We ask for 9 days of MuSR beamtime for the proposed study.
DOI: 10.5286/isis.e.rb1670562
title: Spin Fragmentation in Nd2Ir2O7 and its carrier-doped dependence

description: Nd2Ir2O7 stands out as a fascinating system among pyrochlore iridates because of its potential for realizing a new topological semimetal state which its emergence strongly depend on the magnetic ordering. The all-in/all-out type ordering has been discussed to realize in Nd2Ir2O7 where a reduction in the Nd magnetic moment was observed due to a strong Nd fluctuations. In the case of hole-doped Nd2Ir2O7, our preliminary ZF-µSR observed an enhancement of internal fields at muon sites at low temperature indicating that the hole-doping affects to the suppression of Nd-spin fluctuations. In order to investigate dynamics fluctuations of Nd spins, further longitudinal-field µSR is indispensable.
DOI: 10.5286/isis.e.rb1700044
title: Chemical disorder and network structure of glassy As2Te3

description: Telluride glassy systems are widely used for phase-change optical recording.  They are also promising materials for far-IR applications.  The atomic structure of telluride glasses is much less known compared to their sulphide and selenide counterparts.  A typical example is glassy As2Te3, which exhibits a significant chemical disorder, characterized by homopolar As-As and Te-Te bonds.  Recently, high-pressure experiments using glassy As2Te3 have shown a number of unusual phenomena.  Surprisingly, our high-energy X-ray diffraction measurements have shown a distinct decrease of homopolar bonds in g-As2Te3, recovered from 8.5 GPa, while an increase of chemical disorder at high pressure was expected.  Neutron diffraction measurements are complementary to X-ray scattering results for this particular system and will allow a detailed structural model for g-As2Te3 to be constructed.
DOI: 10.5286/isis.e.rb1710081
title: Probing Low Dimensional Magnetism in Lanthanide Formate Magnetocalorics

description: Low dimensional magnetism provides a crucial playground for the discovery and exploitation of unconventional behaviour. Coordination frameworks have a tendency to adopt highly anisotropic structures making them ideal platforms for such properties. Lanthanide formate frameworks have demonstrated significant potential as paramagnetic magnetocalorics for low temperature cooling applications and we have recently shown that tuning the 1D magnetic interactions in these compounds from antiferromagnetic in Gd(HCO2)3 to ferromagnetic in Tb(HCO2)3 improves performance at higher temperatures. This proposal aims to examine magnetic correlations in the paramagnetic phases of the six other Ln(CHO2)3 frameworks that are accessible to neutron scattering. This will enable us to explore how magnetic interactions change with electronic configuration and how this in turn affects magnetocaloric efficiency.
DOI: 10.5286/isis.e.rb1710094
title: Clarifying the interaction between cyclic oxime and acidic silanols in hierarchical SAPO-34 and AlPO-5 for the Beckmann rearrangement

description: Caprolactam (CL) is a high-value chemical and precursor to nylon-6. Industrially, a harsh, liquid acid catalyst transforms C6-oxime to CL but due to the risk and inefficiency of the process, a solid-acid alternative is desirable. Whilst silicoaluminophosphates (SAPOs) have been successful in this domain, their small micropores suffer mass transport limitations. Hierarchically-porous (HP) SAPOs contain an auxiliary mesoporous network generated by soft-templating with surfactant. As well as improved mass transport, the synthesis introduces pendant silanols in the mesopores, with their own catalytic potential. Interestingly, earlier INS studies revealed the loss of oxime and catalyst O-H modes, indicating that the silanols can interact with oxime at low temperature, in a solid-state mixture. Our aim is to clarify the nature of these interactions and to investigate the loss of the O-H bands.
DOI: 10.5286/isis.e.rb1710124
title: Adsorption versus aggregation; Particles and surface of matching material

description: The balance between particle-surface and particle-particle interactions is entropically driven.   We would like to investigate wherever a multiplayer layer adsorption on a hydrophobic surface for thermal responsive NIPAM nanogels is preferred as concentration increases.
DOI: 10.5286/isis.e.rb1710137
title: Study of Deep Eutectic Solvents dilutions: nanometer size domains and molecular re-organization  Part II

description: Carbon materials with nanopore structures are of great importance for development of energy storage and gas adsorption devices. The critical parameter is pore size and it is difficult to predict.Our group is focused on preparing such carbons from solvents that contains a carbon precursor and does not contain water, the so called deep eutectic solvents (DES). DES are mixed with a water solution of formaldehyde to form a polymer that after carbonization generates the porous carbon. We have hypothesized that pores come from the formation of DES-water nanodomains when the DES is mixed with the water solution. H NMR and Brillouin spectroscopy of water-DES mixtures and simulations seem to agree with the hypothesis. Just by using neutron diffraction to analyse the mixtures would be possible to address this really interesting issue that could allow usto easily predict pore sizes of carbons.
DOI: 10.5286/isis.e.rb1710219
title: Interface of heavy metal layer on a ferromagnetic insulator by PNR

description: In the spin Seebeck effect (SSE), a temperature gradient generates a pure spin current in a ferromagnet. The magnetic insulator yttrium iron garnet Y3Fe5O12 (YIG) covered with a heavy metal (HM), such as Pt, is just a typical example. However, the mechanism of SSE still remains debatable because some of experiments exhibit the ferromagnetic characteristics in thin Pt films on the ferromagnetic insulator due to the magnetic proximity effects. In our previous preliminary PNR study (Xpress proposal performed in May 2016), the PNR data exhibits new route to investigate the origin of the SSE in HM/YIG. Here, we wish to use PNR to measure the magnetic properties of the interface of YIG/HM. The PNR data will allow us to develop a clear model to help explain the SSE in YIG/HM systems.
DOI: 10.5286/isis.e.rb1710229
title: Superconducting intercalates of FeSe tuned in situ with ammonia

description: We propose to study two phases of Na-NH3 intercalated FeSe which have distinct values of Tc, both close to 40 K, but different concentrations of NH3 and quite distinct crystal structures.  We will perform the chemical transformation between these two phases in situ on the muon beam line.  We will use transverse-field muon-spin rotation to probe these two phases in detail and extract information about the superconducting ground state.  We will also demonstrate that the transformation, which is effected by absorption and desorption of ammonia, can be carried out reversibly.
DOI: 10.5286/isis.e.rb1710271
title: Structure of sustainable lead-free low-melting vanadate glass by neutron and x-ray diffraction

description: V2O5 based glass with a sealing temperature of around 400ºC is now being applied in electronic devices, such as in crystal oscillators and MEMS devices as an alternative sealant to the toxic low-melting point glass containing lead and fluorine, or gold-tin solder. We have developed Ag2O-V2O5-TeO2 glass system with a sealing temperature of 200-300ºC. However, structure of Ag2O-V2O5-TeO2 is still unknown and hence it is necessary to reveal the relationship between atomistic and electronic structure of the glass and function, which connection can provide crucial information for designing novel materials. Here we propose neutron diffraction measurements on ternary and quaternary vanadium oxide glasses in order to derive reliable structural information with a high real-space resolution.
DOI: 10.5286/isis.e.rb1720169
title: Superconductivity and the FμF state in ACa2Fe4As4F2

description: Materials with a layered structure have been the subject of great interest as potential candidates for high-temperature superconductors.  The ACa2Fe4As4F2 family of materials crystallise in a body-centred tetragonal lattice containing asymmetric double layers of Fe2As2 separated by insulating CaF2 layers.  This experiment will provide a detailed investigation of the effect of structural changes on the superfluid stiffness in this family of materials as the cation A is varied. It will also examine the relationship between superconductivity and the FμF state that we think is likely to occur in these materials.
DOI: 10.5286/isis.e.rb1720403
title: Local structure of candidate hybrid improper ferroelectrics

description: Ferroelectrics are materials that exhibit a switcheable polarisation, i.e. a net displacement of positively charged cations relative to anions that is reversible. In traditional "proper" ferroelectrics, this property is usually associated with the electronic structure of particular cations, but the field has been shaken recently by the discover of the "hybrid-improper" mechanism for ferroelectricity, in which different types of structural changes can be coupled to give rise to this property. We've been working on some materials with the potential to show ferroelectricity by this new mechanism, but our experiments have revealed some disorder in their crystal structures. We believe that this disorder is related to the very same structural changes associated with the mechanism, and neutron scattering experiments to study this are needed to fully understand this behaviour.