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The rare-earth triangular-lattice chalcogenide is a great platform for exploring both spin liquids and novel magnetic orders with anisotropic spin interactions and magnetic frustrations. Here, we report the thermodynamic and neutron scattering measurements of rare-earth triangular-lattice chalcogenide KErSe$_{2}$, using single-crystal samples. Our experiments revealed a long-range stripe order below 0.2 K. Although the magnetic order was three-dimensional, magnetic excitations exhibited negligible modulation along the z direction, indicating very weak interlayer coupling. Furthermore, magnetic excitation developed a well-defined spin-wave dispersion with a gap of $\sim$0.03 meV at M points. Both the stripe order and spin-wave excitations could be quantitatively understood from the anisotropic spin interactions of the Er$^{3+}$ Kramers doublets.

When the transition temperature of a continuous phase transition is tuned to absolute zero, new ordered phases and physical behaviour emerge in the vicinity of the resulting quantum critical point. Sr3Ru2O7 can be tuned through quantum criticality with magnetic field at low temperature. Near its critical field Bc it displays the hallmark T-linear resistivity and a \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$T\,{{{{{{\mathrm{log}}}}}}}\,(1/T)$$\end{document}Tlog(1/T) electronic heat capacity behaviour of strange metals. However, these behaviours have not been related to any critical fluctuations. Here we use inelastic neutron scattering to reveal the presence of collective spin fluctuations whose relaxation time and strength show a nearly singular variation with magnetic field as Bc is approached. The large increase in the electronic heat capacity and entropy near Bc can be understood quantitatively in terms of the scattering of conduction electrons by these spin-fluctuations. On entering the spin-density-wave ordered phase present near Bc, the fluctuations become stronger suggesting that the order is stabilised through an “order-by-disorder” mechanism., Sr3Ru2O7 exhibits a quantum critical point tunable by magnetic field and has been widely used in the study of criticality. Here, by using inelastic neutron scattering, the authors measure collective magnetic excitations near the quantum critical point and relate them to thermodynamic properties and spin density wave order.

The magnetic Hamiltonian of the Heisenberg quantum antiferromagnet $\mathrm{Sr}\mathrm{Cu}{\mathrm{Te}}_{2}{\mathrm{O}}_{6}$ is studied by inelastic neutron scattering technique on powder and single-crystalline samples above and below the magnetic transition temperatures at 8 and 2 K. The high-temperature spectra reveal a characteristic diffuse scattering corresponding to a multispinon continuum, confirming the dominant quantum spin chain behavior due to the third neighbor interaction ${J}_{\text{intra}}=4.22$ meV (49 K). The low-temperature spectra exhibit sharper excitations at energies 1.25 meV, which can be explained by considering a combination of weak antiferromagnetic first nearest neighbor interchain coupling ${J}_{1}=0.17$ meV ($1.9$ K) and even weaker ferromagnetic second nearest neighbor ${J}_{2}=\ensuremath{-}0.037$ meV ($\ensuremath{-}0.4$ K) or a weak ferromagnetic ${J}_{2}=\ensuremath{-}0.11$ meV ($\ensuremath{-}1.3$ K) and antiferromagnetic ${J}_{6}=0.16$ meV ($1.85$ K), giving rise to the long-range magnetic order and spin-wave excitations at low energies. These results suggest that $\mathrm{Sr}\mathrm{Cu}{\mathrm{Te}}_{2}{\mathrm{O}}_{6}$ is a highly one-dimensional Heisenberg system with three mutually perpendicular spin chains coupled by a weak ferromagnetic ${J}_{2}$ in addition to the antiferromagnetic ${J}_{1}$ or ${J}_{6}$, presenting a contrasting scenario from the highly frustrated hyper-hyperkagome lattice (equally strong antiferromagnetic ${J}_{1}$ and ${J}_{2}$) found in the isostructural quantum spin liquid candidate $\mathrm{Pb}\mathrm{Cu}{\mathrm{Te}}_{2}{\mathrm{O}}_{6}$ .

We present an experimental study of the magnetic structure and dynamics of two frustrated hyperkagome compounds, Gd3Ga5O12 and Gd3Al5O12. It has previously been shown that Gd3Ga5O12 exhibits long-range correlations of multipolar directors, that are formed from antiferromagnetic spins on loops of ten ions. Using neutron diffraction and Reverse Monte Carlo simulations we prove the existence of similar magnetic correlations in Gd3Al5O12, showing the ubiquity of these complex structures in frustrated hyperkagome materials. Using inelastic neutron scattering we shed further light on the director state and the associated low lying magnetic excitations. In addition we have measured quasielastic dynamics that show evidence of spin diffusion. Finally, we present AC susceptibility measurements on both Gd3Ga5O12 and Gd3Al5O12, revealing a large difference in the low frequency dynamics between the two otherwise similar compounds., Comment: 13 pages, 12 figures, Accepted by Physical Review B

The authors report inelastic neutron scattering measurements to directly visualize the effects of collective quantum fluctuations in a spin-\textonehalf{} near-Heisenberg antiferromagnet on a triangular lattice. They observe a rich spectrum of sharp magnons at low energies with strongly renormalized dispersions and much reduced spectral weight, which are accompanied at higher energies by a very strong and highly structured continuum of excitations. The dispersion renormalizations and transfer of spectral weight to continuum states are attributed to the effect of quantum fluctuations and interactions beyond the spin-wave approximation.

The combination of neutron time-of-flight spectroscopy and longitudinal polarization analysis opens up the possibility of simultaneously separating cross-section components over vast regions in ( Q , Δ E ) space. In this paper, we describe initial results of a project to install longitudinal polarization analysis on the LET cold neutron spectrometer at the ISIS Neutron and Muon Facility; namely, the design and commissioning of the polarizing primary spectrometer. The polarized neutron beam is generated by a supermirror-based transmission device, for which ray tracing simulations indicate a high neutron polarization P ∼ 96 % and transmission T ∼ 40 % . Despite the short distance between this device and the precession coil flipper, and the consequent large stray magnetic fields on the latter, careful optimization of the field environment yields predictions of excellent flipping performance ∼ 99 % . Both simulation results are confirmed via measurements using a polarizing Cu2MnAl Heusler crystal as an analyzer.

The aim of the Target Station 1 (TS-1) project at the ISIS Neutron and Muon Source is a complete refurbishment of the internals of the TS-1, including the design of the target and its cooling systems, the moderators, the reflector and all their associated services. The main reason for this refurbishment is to secure the future of the, 30 years old, ISIS Target Station 1. In this paper, the neutronics analysis of possible improvements of ISIS TS-1 is described. The goal is to deliver a new model of Target Station 1 which maintains the instruments pulse time characteristics within the limits defined by instrument scientists and provides the largest collective gain. A number of the MCNPX models of the TS-1 future TRaM assembly have been prepared and optimized by ISIS neutronics team using the CombLayer package. New models have been benchmarked against a baseline TS-1 model taking into account flux and time distribution of all existing TS-1 instruments. The best model, described in this paper, shows that significant benefits (operational improvements, additional flexibility and neutron flux increase) can be achieved without modification of existing instruments.

SHERPA is a proposed quasielastic neutron spectrometer with polarisation analysis, intended to replace the ageing Iris instrument at the ISIS neutron and muon source. In this paper we present a concept of the instrument along with Monte-Carlo simulations and analysis of possible instrument location. We expect greatly increased count rate compared to Iris (expected from 49 to 660 × Iris) in unpolarised mode and dedicated polarisation analysis capabilities at a more modest count rate increase (~5-70 × Iris). This huge gain in the count rate would be achieved from the combination of three factors: modern neutron guide with high-m coating, and prismatic effect and larger solid angle coverage at the energy analyser. Such an instrument would be the first of its kind and has incredible potential to revolutionise quasielastic neutron scattering technique through the separation of the coherent and incoherent scattering contributions.

Aerial photography and reconnaissance for archaeology was pioneered in the Middle East a century ago. This article highlights the work of the Aerial Archaeology Project in the northern and eastern ...

Complex bound states of magnetic excitations, known as Bethe string, were predicted almost a century ago to exist in one-dimensional quantum magnets 1. The dispersions of the string states have so far remained the subject of intensive theoretical studies 2-7. By performing neutron scattering experiments on the one-dimensional Heisenberg-Ising antiferromagnet SrCo2V2O8 in high longitudinal magnetic fields, we reveal in detail the dispersion relations of the string states over the full Brillouin zone, as well as their magnetic field dependences. Furthermore the characteristic energy, the scattering intensity and linewidth of the observed string states exhibit excellent agreement with our precise Bethe Ansatz calculations. Our results establish the important role of string states in the quantum spin dynamics of one-dimensional systems, and will invoke studies of their dynamical properties in more general many-body systems., Main manuscript: 6 pages, 4 figures, Supplementary information: 8 pages, 6 figures, 1 table

The quasi-two-dimensional Heisenberg spin $S=1/2$ dimer system bis(2-amino-5-fluoro-pyridinium) tetrachlorocuprate(II) is studied by means of inelastic neutron scattering, calorimetry, and nuclear magnetic resonance (NMR) experiments. In the absence of an applied magnetic field we find dispersive triplet excitations with a spin gap of $\mathrm{\ensuremath{\Delta}}=1.112(15)$ meV and a bandwidth of 0.715(15) meV within the layers and 0.116(15) meV between the layers, respectively. In an applied magnetic field of ${\ensuremath{\mu}}_{0}{H}_{c}\ensuremath{\approx}8.5$ T the spin gap is closed and we find a field-induced antiferromagnetically ordered phase.

This paper presents a concept for a new type of in-direct time of flight cold neutron spectrometer called Mushroom. Mushroom has a unique pyrolytic graphite (PG) analyser/position sensitive detector geometry enabling a massive 2 π steradians of continuous position sensitive detector coverage, emulating some of its direct geometry counterparts such as IN5 or LET. It has many advantages over its direct geometry cousins though, being much more compact and much less expensive to build, but its biggest advantage is the order of magnitude larger count rates for the same resolution. It is envisaged it will be used to map out the 4 dimensional S ( Q , ω ) of single crystals in a matter of hours rather than days. Its design is aimed at minimising background and also uniquely allows easy selection of analyser reflection order PG002 or PG004. This paper presents details of the design along with full simulations of its potential performance using ray tracing software.

The adsorption of water in one-dimensional channels in porous aluminophosphate material AlPO4-5 has been studied by a combination of gravimetric analysis techniques, neutron and X-ray diffraction and neutron spectroscopy. Molecular structure of AlPO4-5 consists of 12-membered rings of alternating, corner-sharing AlO4 and PO4 tetrahedra connected by oxygen bridges into sheets in the (a, b) plane. The sheets are connected by oxygen bridges along the c crystal axis and form one-dimensional channels of which the largest, formed by the 12-membered rings, have a van der Waals diameter of about 8.3 A. Gradually increasing the amount of adsorbed water we could follow the evolution of the confined water mobility in a systematic way and identify the molecular mechanism of water adsorption. We focused particularly on the range of low and medium relative pressures up to p/p0 = 0.32, where a change from a hydrophobic behavior to a steep, capillary condensation like water intake has been observed. At the initial adsorption stages water occupies positions close to the pore walls causing the contraction of channels in the (a, b) plane and the prolongation of the channels along c axis in AlPO4-5. With the progressing intake water molecules form chains along the main channels. The cooperative interactions between water molecules lead to the onset of phonon-like cooperative modes and, surprisingly, to the increase of diffusive-like motion, which slow down only in the final adsorption stages when AlPO4-5 channels are completely filled.

We report on the design and construction of a neutron polarization analyzer based on a 3He spin filter for the LET spectrometer at the ISIS facility. Its commissioning completes the uniaxial polarized mode of the instrument. Besides the 3He spin filter cell, the analyzer consists of a set of electromagnetic coils to provide a uniform magnetic field, and a collimator to eliminate background from the sample environment and analyzer infrastructure. The 3He cell is separated from the LET main tank vacuum by means of a gas tank, which permits rapid cell changeovers and guarantees safe operation. In addition to the analyzer hardware, software has been written to reduce and correct polarized data. The successful operation of the polarized mode was realized for the separation of coherent and incoherent dynamics in an organic solar cell polymer blend.

Solvent diffusion in a prototypical supramolecular gel probed by quasi-elastic neutron scattering on the picosecond timescale is faster than that in the respective bulk solvent. This phenomenon is hypothesized to be due to disruption of the hydrogen bonding of the solvent by the large hydrophobic surface of the gel network.

The regions of Northern Mesopotamia and the Levant, covering parts of modern-day southern Turkey, Syria, northern Iraq, Lebanon, Jordan, Israel, and Palestine, consist of an extremely varied climat...

The MAPS direct geometry time-of-flight chopper spectrometer at the ISIS pulsed neutron and muon source has been in operation since 1999 and its novel use of a large array of position-sensitive neutron detectors paved the way for a later generations of chopper spectrometers around the world. Almost two decades of experience of user operations on MAPS, together with lessons learned from the operation of new generation instruments, led to a decision to perform three parallel upgrades to the instrument. These were to replace the primary beamline collimation with supermirror neutron guides, to install a disk chopper, and to modify the geometry of the poisoning in the water moderator viewed by MAPS. Together these upgrades were expected to increase the neutron flux substantially, to allow more flexible use of repetition rate multiplication and to reduce some sources of background. Here we report the details of these upgrades, and compare the performance of the instrument before and after their installation, as well as to Monte Carlo simulations. These illustrate that the instrument is performing in line with, and in some respects in excess of, expectations. It is anticipated that the improvement in performance will have a significant impact on the capabilities of the instrument. A few examples of scientific commissioning are presented to illustrate some of the possibilities., Comment: 17 pages, 15 figures

The quantum spin liquid is a highly entangled magnetic state characterized by the absence of static magnetism in its ground state. Instead, the spins fluctuate in a highly correlated way down to the lowest temperatures. Quantum spin liquids are very rare and are confined to a few specific cases where the interactions between the magnetic ions cannot be simultaneously satisfied (known as frustration). Lattices with magnetic ions in triangular or tetrahedral arrangements, which interact via isotropic antiferromagnetic interactions, can generate such a frustration. Three-dimensional isotropic spin liquids have mostly been sought in materials where the magnetic ions form pyrochlore or hyperkagome lattices. Here we present a three-dimensional lattice called the hyper-hyperkagome that enables spin liquid behaviour and manifests in the compound PbCuTe2O6. Using a combination of experiment and theory, we show that this system exhibits signs of being a quantum spin liquid with no detectable static magnetism together with the presence of diffuse continua in the magnetic spectrum suggestive of fractional spinon excitations., Quantum spin liquids have magnetic moments that do not form magnetic order even as the temperature approaches zero, leading to the dominance of quantum fluctuations. Chillal et al. present evidence that the hyper-hyperkagome lattice of PbCuTe2O6 hosts a three-dimensional quantum spin liquid.

At the interface between two distinct materials, desirable properties, such as superconductivity, can be greatly enhanced 1 , or entirely new functionalities may emerge 2 . Similar to in artificially engineered heterostructures, clean functional interfaces alternatively exist in electronically textured bulk materials. Electronic textures emerge spontaneously due to competing atomic-scale interactions 3 , the control of which would enable a top-down approach for designing tunable intrinsic heterostructures. This is particularly attractive for correlated electron materials, where spontaneous heterostructures strongly affect the interplay between charge and spin degrees of freedom 4 . Here we report high-resolution neutron spectroscopy on the prototypical strongly correlated metal CeRhIn5, revealing competition between magnetic frustration and easy-axis anisotropy—a well-established mechanism for generating spontaneous superstructures 5 . Because the observed easy-axis anisotropy is field-induced and anomalously large, it can be controlled efficiently with small magnetic fields. The resulting field-controlled magnetic superstructure is closely tied to the formation of superconducting 6 and electronic nematic textures 7 in CeRhIn5, suggesting that in situ tunable heterostructures can be realized in correlated electron materials. By means of a sensitive neutron spectroscopy approach the magnetic excitations in the heavy fermion superconductor CeRhIn5 are probed, revealing a uniaxial anisotropy that can be tuned with an external magnetic field.

The EAMENA (Endangered Archaeology of the Middle East and North Africa) project is a collaboration between the Universities of Leicester, Oxford and Durham; it is funded by the Arcadia Fund and the Cultural Protection Fund. This paper explores the development of the EAMENA methodology, and discusses some of the problems of working across such a broad region. We discuss two main case studies: the World Heritage site of Cyrene illustrates how the project can use satellite imagery (dating from the 1960s to 2017), in conjunction with published data to create a detailed set of database records for a single site and, in particular, highlights the impact of modern urban expansion across the region. Conversely, the Homs Cairns case study demonstrates how the EAMENA methodology also works at an extensive scale, and integrates image interpretation (using imagery dating from the 1960s to 2016), landuse mapping and field survey (2007–2010) to record and analyse the condition of hundreds of features across a small study region. This study emphasises the impact of modern agricultural and land clearing activities. Ultimately, this paper assesses the effectiveness of the EAMENA approach, evaluating its potential success against projects using crowd-sourcing and automation for recording archaeological sites, and seeks to determine the most appropriate methods to use to document sites and assess disturbances and threats across such a vast and diverse area.

Since its proposal by Anderson, resonating valence bonds (RVB) formed by a superposition of fluctuating singlet pairs have been a paradigmatic concept in understanding quantum spin liquids (QSL). Here, we show that excitations related to singlet breaking on nearest-neighbor bonds describe the high-energy part of the excitation spectrum in YbMgGaO4, the effective spin-1/2 frustrated antiferromagnet on the triangular lattice, as originally considered by Anderson. By a thorough single-crystal inelastic neutron scattering (INS) study, we demonstrate that nearest-neighbor RVB excitations account for the bulk of the spectral weight above 0.5 meV. This renders YbMgGaO4 the first experimental system where putative RVB correlations restricted to nearest neighbors are observed, and poses a fundamental question of how complex interactions on the triangular lattice conspire to form this unique many-body state., Comment: To be published in Nature Communications

There is clear and irrefutable evidence that archaeological and historical sites have the potential to be the catalysts for economic, social, and political change. The issue facing us is how might we understand the conditions which turn the potential into reality. For that to happen we need research into the contribution that heritage makes to social and economic life. This paper provides an overview of this recent research undertaken by the Heritage Lottery Fund. It demonstrates the importance of having good evidence on which to base decisions and develop future policies, but argues that a reliance on the economic case alone is not sufficient. It concludes by suggesting that, in the current economic climate, it will be important for heritage organizations to use the argument for the economic benefits of the heritage within the cultural value context, and with as wide an array of potential supporters as possible and not just national and local governments.

The workshop was made possible by a grant from the Palestine Exploration Fund and took place at the Nabataean Centre for Archaeological Studies, Petra, Al-Hussein Bin Talal University, Jordan betwe...

The effect of uncertainty in chopper phasing (jitter) has been investigated for the high-resolution time-of-flight spectrometer LET at the ISIS second target station. The investigation is carried out using virtual experiments, with the neutron simulation package McStas, where the chopper jitter is found to cause a Lorentzian tail in the resolution function. We find that jitter even up to the unrealistically high value of 2 µs can be tolerated without any noticeable degradation of resolution or incident intensity. The results are supported by simple analytical estimates and are believed to be general for chopper spectrometers.

The whole attitude of this country and of the civilized world in general has changed towards archaeology in recent years. We regard the national monuments to which this Bill refers as part of the h...

A tetranuclear [2 × 2] grid-like manganese(III) Schiff base complex, Mn4, has been synthesized and characterized by single-crystal X-ray crystallography. Direct-current magnetization measurements were performed on the system and proved to be insufficient for an accurate magnetic model to be deduced. Combined inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) experiments provided the necessary information in order to successfully model the magnetic properties of Mn4. The resulting model takes into account both the magnitude and the relative orientations of the single-ion anisotropy tensors.

LET is a new multi-chopper direct geometry cold neutron spectrometer, recently installed on target station 2 (TS2) at the ISIS spallation neutron source. The characteristics of the primary spectrometer are a 25 m straight super-mirror guide viewing the new highly efficient coupled solid methane moderator system. This combination yields a high incident flux of neutrons with a wide dynamic range of 0.6–80 meV. LET employs a novel flux compression guide design which in combination with two 300 Hz counter rotating choppers produces fine energy resolutions of ≥ 0.8 % δ E / Ei , to be realised with very little flux sacrifice compared to conventional methods. The multi-chopper system is designed to make full use of the long 100 ms time frames of TS2, allowing the user to make multiple measurements within a single frame. The secondary spectrometer is characterised by a wide area position sensitive 3He multidetector with π steradians of nearly gapless coverage over the angular range from −40° to +140° in the horizontal plane and ±30° in the vertical plane. The multidetector utilises the worlds first 4 m position sensitive 3He neutron detector tubes. LET has been designed specifically to allow the use of polarised neutrons allowing the user to exploit full XYZ neutron polarisation analysis. In addition a new 9 T magnet has been designed for LET allowing the use of large samples of 25 mm×25 mm with a 30° vertical opening to make use of the large multidetector.

Currently there are two, decoupled and poisoned, water moderators at the ISIS Target Station 1 (TS-1), located above the target, operating at room temperature and providing neutrons for the experiments in the fields of spectroscopy, diffraction, etc. In this paper, the details about neutronics model of ISIS Target Station 1, simulation results related to TS-1 water moderators and comparison with corresponding measurement results are presented. The importance of the quality neutronics calculations for planning the upgrade/changes in the target station (as in removal of the poisoning foil in upstream water moderator) and locating the operational issues (disappearance of poisoning foil in downstream water moderator) is discussed.

As part of the ISIS TS1 project, work has been carried out on the cryogenic hydrogen moderator system, the main focus being understanding and improving the ratio of spin isomers in the liquid hydrogen moderator.

A significant grant from the Packard Humanities Institute has allowed the development of a long-standing project of Aerial Archaeology in Jordan. In 2008 the number of flying hours, sites recorded and associated ground-work time trebled. Hundreds of sites, not previously recorded, have been added to the database. A web-based archive of the entire collection of aerial photos taken since 1997 is now under construction.

Antiferromagnetism is relevant to high temperature (high-Tc) superconductivity because copper oxide and iron arsenide high-Tc superconductors arise from electron- or hole-doping of their antiferromagnetic (AF) ordered parent compounds. There are two broad classes of explanation for the phenomenon of antiferromagnetism: in the local moment picture, appropriate for the insulating copper oxides, AF interactions are well described by a Heisenberg Hamiltonian; while in the itinerant model, suitable for metallic chromium, AF order arises from quasiparticle excitations of a nested Fermi surface. There has been contradictory evidence regarding the microscopic origin of the AF order in iron arsenide materials, with some favoring a localized picture while others supporting an itinerant point of view. More importantly, there has not even been agreement about the simplest effective ground state Hamiltonian necessary to describe the AF order. Here we report inelastic neutron scattering mapping of spin-wave excitations in CaFe2As2, a parent compound of the iron arsenide family of superconductors. We find that the spin waves in the entire Brillouin zone can be described by an effective three-dimensional local moment Heisenberg Hamiltonian, but the large in-plane anisotropy cannot. Therefore, magnetism in the parent compounds of iron arsenide superconductors is neither purely local nor purely itinerant; rather it is a complicated mix of the two., 18 pages, 4 figures; Nature Physics (2009) In press

The authors have provided some of Antiquity's most stunning frontispieces since we introduced them in 2006. We asked them to show how aerial archaeology has developed in Jordan over some 90 years, tell us about the techniques and approaches used and its potential here and in other desert and mountainous lands.

The dynamic magnetic response of the intermediate-valence compound EuCu2Si2 has been studied using inelastic neutron scattering. At low temperatures, strong renormalization of the 7F0 → 7F1 spin-orbit transition energy is detected; it is likely to be related to partial delocalization of the f electrons of Eu. An increase in the temperature increases the valence instability of europium and results in further changes in the magnetic excitation spectrum parameters and the appearance of an intense quasi-elastic component.

UPd 3 exhibits four phase transitions below T 0 = 7.8 K , attributed to a succession of antiferroquadrupolar (AFQ) orderings of the 5 f 2 uranium ions localised on the quasi-cubic sites of the dhcp crystal structure. From earlier polarised neutron diffraction measurements in a magnetic field, we proposed that the order parameter of the phase below T 0 is Q x 2 - y 2 and a model for the order parameters of the four phases was subsequently developed. This model has now been tested experimentally with measurements of the azimuthal dependence of the intensities of the quadrupolar reflections in the different phases, by means of X-ray resonant scattering (XRS) studies at ESRF. The results indicate that the order parameter, in zero field, of the phase below T 0 is Q zx . Our model provides an explanation for these apparently contradictory results. New measurements of the heat capacity of UPd 3 at low temperatures have revealed the entropy changes at each of the four transitions. We find that the entropy changes ( Δ S ) at T 0 and T + 1 = 6.9 K are minimal, whereas Δ S is large at T - 1 = 6.7 K . From this information together with the new XRS results, we have extended our model to provide an explanation of the AFQ structures of UPd 3 .

We have studied nanoscale diffusion of membrane hydration water in fluid-phase lipid bilayers made of 1,2-dimyristoyl-3-phosphocholine (DMPC) using incoherent quasi-elastic neutron scattering. Dynamics were fit directly in the energy domain using the Fourier transform of a stretched exponential. By using large, 2-dimensional detectors, lateral motions of water molecules and motions perpendicular to the membranes could be studied simultaneously, resulting in 2-dimensional maps of relaxation time, τ, and stretching exponent, β. We present experimental evidence for anomalous (sub-diffusive) and anisotropic diffusion of membrane hydration water molecules over nanometer distances. By combining molecular dynamics and Brownian dynamics simulations, the potential microscopic origins for the anomaly and anisotropy of hydration water were investigated. Bulk water was found to show intrinsic sub-diffusive motion at time scales of several picoseconds, likely related to caging effects. In membrane hydration water, however, the anisotropy of confinement and local dynamical environments leads to an anisotropy of relaxation times and stretched exponents, indicative of anomalous dynamics.

The phonon dispersion in RB12 (R = Yb, Lu) systems is studied in detail using inelastic neutron scattering over a wide range of energies (up to 55 meV). It is demonstrated that the main features of the lattice dynamics in the RB12 crystals can be described in terms of a simple model of force constants with a strong hierarchy of interatomic interactions in the systems: B-B ≫ B-R ≫ R-R. An interesting feature of the low-energy portion of the phonon spectrum is the weakly dispersive optical mode. According to the model calculations, this mode is associated with the relative displacements and “breathing” vibrations of the boron nanoclusters B12.

To clarify the role of Yb–Yb correlations in the formation of the gap-like excitation spectrum of YbB 12 , the spin dynamics of strongly diluted Yb 0.25 Lu 0.75 B 12 have been studied by inelastic neutron scattering in a wide temperature range. The data indicate that the spin gap is not suppressed by the dilution process even for large concentrations of Lu. However, the breaking-down of the Yb-sublattice periodicity leads to a strong smearing of the low-energy features and to a moderate suppression of the high-energy peak in the magnetic spectral response of YbB 12 . The interrelation of the spin and charge gaps is discussed.

We report on unusual non-Fermi liquid features of the ternary compound CeNi 9 Ge 4 which exhibits the largest ever recorded value of the electronic specific heat C / T ≃ 5.5 J / mol K 2 at T = 0.08 K in a purely paramagnetic system. The latter is confirmed by μ SR measurements down to 30 mK revealing a rather slow simple exponential muon spin depolarisation in zero-field and thus a spatially homogeneous paramagnetic state. The ground state properties and crystal field (CF) splitting of CeNi 9 Ge 4 have been studied by specific heat, magnetic susceptibility as well as muon spin relaxation ( μ SR) and inelastic neutron spectroscopy (INS).

Lidar (Light Detection and Ranging), which has recently come into use for airborne environmental monitoring, is now beginning to find success in archaeological survey. Liaison between the Environment Agency and English Heritage has led to a lidar survey of the Stonehenge landscape, where new sites have been discovered, known ones extended and its potential as an important new tool for the management of archaeological landscapes is discussed for the first time. Lidar has the potential to radically transform our future understanding and management of the historic environment. The article by Devereux et al. (pages 648-660 of this volume) shows the technique applied to woodland.

Aerial photography for archaeology has been developing its approaches and techniques over the past 100 years so that it now integrates the results of reconnaissance with extensive interpretative and analytical surveys. This paper introduces the philosophy and approach of the English Heritage (EH) Aerial Survey team, covering aerial reconnaissance and the National Mapping Programme (NMP), as well as the potential developments and opportunities in Europe. In the 1980s there was a debate over the nature of the evidence derived from aerial photographs, especially how to describe archaeological features. As part of NMP a classification and recording system has been devised which meets most of the users’ needs, be they national organisations, county archaeologists, commercial contractors or university-based researchers. The maps and records produced by NMP are used to further our understanding of the past human settlement in England, not only at the individual site level, but also in regional or landscape contexts. This paper provides an overview of the current progress of NMP and acts as an entree for explaining the current research and recording of archaeological landscapes throughout Europe. Recent developments in Britain and Europe have provided the opportunity for a greater priority to be given to aerial survey and accelerating programmes of mapping. In Europe the ending of the cold war has allowed greater access to aerial photographs and the possibility of beginning new reconnaissance, as well as introducing new forms of remote sensing. All these developments have led to a transformation of our understanding of prehistoric, Roman and medieval archaeology. Resume L'emploi des photographies aeriennes pour l'archeologie s'est developpe au cours des cent dernieres annees au point d'arriver maintenant a integrer techniquement les resultats de la reconnaissance classique avec les releves analytiques et interpretatifs concernant de grandes etendues. On aborde dans cet article la methode et la philosophie de l’equipe de leve aerien du service du Patrimoine anglais, en y incluant la reconnaissance aerienne et le programme national de cartographie (NMP), ainsi que les possibilites et les occasions de developpement en Europe. Il y a eu dans les annees 1980 un debat sur la nature des temoignages apportes par les photographies aeriennes, en particulier sur la facon de decrire les elements archeologiques. On a pu concevoir, dans le cadre du NMP, un systeme d'enregistrement et de classification qui satisfait la plupart des besoins des usagers, qu'il s'agisse d'organismes nationaux, d'archeologues dans les comtes, de contractants commerciaux ou de chercheurs universitaires. L'emploi des enregistrements et des cartes etablies par le NMP facilite notre comprehension des implantations humaines du passe en Angleterre, non seulement au niveau d'un site individuel, mais aussi dans leur contexte paysager ou regional. On fournit dans cet article un apercu des progres actuels du NMP et une cle permettant d'expliquer les recherches en cours en Europe et les saisies sur les paysages archeologiques. Les developpements recents effectues en Angleterre comme en Europe ont permis d'accorder une priorite plus grande aux leves aeriens et ont accelere les programmes de cartographie. La fin de la guerre froide a ouvert en Europe un acces bien plus grand aux photographies aeriennes et permet d'entreprendre de nouvelles reconnaissances et de recourir egalement a de nouvelles formes de teledetection. Tous ces developpements nous ont amenea modifier notre comprehension de l'archeologie pre-historique, romaine et medievale. Zusammenfassung Die Luftbildphotographie fur die Archaologie hat in den letzten einhundert Jahren ihre Ansatze und Techniken so weit fortentwickelt, dass sie heutzutage die Erkundungsergebnisse mit ausfuhrlichen Interpretationen und analytischen Untersuchungen erganzt. Dieser Beitrag fuhrt in die Philosophie und die Vorgehensweise der Arbeitsgruppe fur Luftbildvermessung des staatlichen Denkmalschutzes ein. Es werden die Erkundung aus der Luft und das Nationale Kartierprogramm (NMP), sowie weitere potentielle Entwicklungen und Moglichkeiten in Europa vorgestellt. In den 80er Jahren des 20. Jahrhunderts gab es eine Debatte uber die Art der Nachweise, die aus Luftbildern gewonnen werden konnen, insbesondere daruber, wie archaologische Merkmale beschrieben werden konnen. Als Teil des nationalen Kartierprogramms wurde ein Klassifizierungs- und Erfassungssystem ausgedacht, das die meisten Nutzeranforderungen erfullt, seien es nationale Organisationen, Archaologen auf Kreisebene, kommerzielle Anbieter oder universitare Forscher. Die Karten und Dokumente, die durch NMP produziert werden, werden zur Vertiefung unseres Wissens uber fruhere Besiedelung in England, nicht nur an individuellen Orten, sondern auch im regionalen oder Landschaftskontext verwendet. Dieser Beitrag gibt einen Uberblick uber den aktuellen Fortschritt von NMP und fuhrt erklarend in die aktuelle Forschung und Erfassung archaologischer Landschaften in Europa ein. Jungste Entwicklungen in Grosbritannien und Europa haben die Moglichkeit eroffnet, dass die Luftbildvermessung mit hoherer Prioritat zur Beschleunigung von kartographischen Programmen eingesetzt wird. Durch das Ende des Kalten Krieges in Europa ist sowohl der Zugang zu Luftbildern erweitert worden, als auch die Moglichkeiten geschaffen worden, neue Erkundungen durchzufuhren und neuen Formen der Fernerkundung anzuwenden. All diese Entwicklungen haben dazu beigetragen, unser Verstandnis der prahistorischen, romischen und mittelalterlichen Geschichte zu verandern.

High energy transfer inelastic neutron scattering has been used to investigate the temperature dependence in the range from 20 to 450 K of the intermultiplet transition E inter in the intermetallic compound Sm 2 Fe 17 . The peak due to this transition, observed in the inelastic neutron spectrum, shifts to lower energies with increasing temperature. From the temperature dependence of E inter , the temperature dependence of the exchange field B ex acting on the Sm ion has been established experimentally, as the energy of the intermultiplet transition provides a direct value for the exchange field. At the highest measured temperature T =450 K, which is above the Curie point of 389 K for this compound, the transition energy is situated just above the bare spin–orbit splitting for Sm 3+ . The method utilized in the present investigation offers a rather easy and direct way to determine B ex in a large range of Sm intermetallics, which form an interesting class of hard magnetic materials.

A new type of disk chopper neutron monochromator for time of flight spectrometers is presented. It combines both the multiple slits and the neutron beam compression methods such that the incident beam is split into two, with both halves being compressed in parallel before going though two separate slits in a set of counter-rotating disk choppers. The two beams are then recombined to give a smooth beam profile at the sample position. Compressing and chopping two parallel beams allows one to obtain the same neutron burst time, and hence energy resolution, with twice the beam width and hence twice the neutron intensity of the usual single beam methods.

We present a design for implementing uniaxial polarisation analysis on the LET cold neutron time-of-flight spectrometer, installed on the second target station at ISIS. The polarised neutron beam is to be produced by a transmission-based supermirror polariser with the polarising mirrors arranged in a "double-V" formation. This will be followed by a Mezei-type precession coil spin flipper, selected for its small spatial requirements, as well as a permanent magnet guide field to transport the beam polarisation to the sample position. The sample area will contain a set of holding field coils, whose purpose is to produce a highly homogenous magnetic field for the wide-angle 3He analyser cell. To facilitate fast cell changes and reduce the risk of cell failure, we intend to separate the cell and cryostat from the vacuum of the sample tank by installing both in a vessel at atmospheric pressure. When the instrument upgrade is complete, the performance of LET is expected to be commensurate with existing and planned polarised cold neutron spectrometers at other sources. Finally, we discuss the implications of performing uniaxial polarisation analysis only, and identify quasi-elastic neutron scattering (QENS) on ionic conducting materials as an interesting area to apply the technique.

The conduction electrons in a metal experience competing interactions with each other and the atomic nuclei. This competition can lead to many types of magnetic order in metals. For example, in chromium the electrons order to form a spin-density-wave (SDW) antiferromagnetic state. A magnetic field may be used to perturb or tune materials with delicately balanced electronic interactions. Here we show that the application of a magnetic field can induce SDW magnetic order in a metal, where none exists in the absence of the field. We use magnetic neutron scattering to show that the application of a large (~8T) magnetic field to the metamagnetic perovskite metal Sr3Ru2O7 can be used to tune the material through two magnetically-ordered SDW states. The ordered states exist over relatively small ranges in field (, Legend in Fig. 3(b) corrected