Classical spin liquid or extended critical range in h-YMnO3_3?

Inelastic neutron experiments on the classical triangular-lattice geometrically frustrated antiferromagnet h-YMnO$_3$ reveal diffuse, gapless magnetic excitations present both below and far above the ordering temperature, $T_N$. The correlation length of the excitations increases as the temperature approaches zero, bearing strong resemblance to critical scattering. We model the scattering as critical spin-spin correlations in a two-dimensional magnetic ground state, and we speculate that this may provide a general framework to understand features typically attributed to classical spin liquids

Design and performance of the multiplexing spectrometer CAMEA

The cold neutron multiplexing secondary spectrometer CAMEA (Continuous Angle Multiple Energy Analysis) was commissioned at the Swiss spallation neutron source SINQ at the Paul Scherrer Institut at the end of 2018. The spectrometer is optimised for an efficient data collection in the horizontal scattering plane, allowing for detailed and rapid mapping of excitations under extreme conditions. The novel design consists of consecutive, upward scattering analyzer arcs underneath an array of position sensitive detectors mounted inside a low permeability stainless-steel vacuum vessel. The construction of the world's first continuous angle multiple energy analysis instrument required novel solutions to many technical challenges, including analyzer mounting, vacuum connectors, and instrument movement. These were solved by extensive prototype experiments and in-house developments. Here we present a technical overview of the spectrometer describing in detail the engineering solutions and present our first experimental data taken during the commissioning. Our results demonstrate the tremendous gains in data collection rate for this novel type of spectrometer design

Prototype of the novel CAMEA concept—A backend for neutron spectrometers

The continuous angle multiple energy analysis concept is a backend for both time-of-flight and analyzer-based neutron spectrometers optimized for neutron spectroscopy with highly efficient mapping in the horizontal scattering plane. The design employs a series of several upward scattering analyzer arcs placed behind each other, which are set to different final energies allowing a wide angular coverage with multiple energies recorded simultaneously. For validation of the concept and the model calculations, a prototype was installed at the Swiss neutron source SINQ, Paul Scherrer Institut. The design of the prototype, alignment and calibration procedures, experimental results of background measurements, and proof-of-concept inelastic measurements on LiHoF4 and h-YMnO3 are presented here

Lack of the purinergic receptor P2X7 results in resistance to contact hypersensitivity

Engagement of P2X7 on mouse dendritic cells, presumably by ATP released in response to contact allergen, is needed for IL-1β production and the sensitization phase of contact hypersensitivity

MJOLNIR:A software package for multiplexing neutron spectrometers

Novel multiplexing triple-axis neutron scattering spectrometers yield significant improvements of the common triple-axis instruments. While the planar scattering geometry keeps ensuring compatibility with complex sample environments, a simultaneous detection of scattered neutrons at various angles and energies leads to tremendous improvements in the data acquisition rate. Here we report on the software package MJOLNIR that we have developed to handle the resulting enhancement in data complexity. Using data from the new CAMEA spectrometer of the Swiss Spallation Neutron Source at the Paul Scherrer Institut, we show how the software reduces, visualises and treats observables measured on multiplexing spectrometers. The software package has been generalised to a uniformed framework, allowing for collaborations across multiplexing instruments at different facilities, further facilitating new developments in data treatment, such as fitting routines and modelling of multi-dimensional data

Nanocriticality in the magnetic phase transition of CoO nanoparticles

The universal theory of critical phase transitions describes the critical behavior at second-order phase transitions in infinitely large systems. With the increased contemporary interest in nanoscale materials, we investigated CoO nanoparticles by means of neutron scattering and found how the theory of critical phenomena breaks down in the nanoscale regime. Using CoO as a model system, we have identified a size-dependent nanocritical temperature region close to the antiferromagnetic phase transition where the magnetic correlation length of the nanoparticles converges to a constant value, which is significantly smaller than that of the saturated state found at low temperatures. This is in clear contrast to the divergence around $T_{\rm N}$ observed for bulk systems. Our findings of nanocriticality in the magnetic phase transition is of great importance for the understanding of phase transitions at the nanoscale

Dataset package for the manuscript "A microscopic Kondo lattice model for the heavy fermion antiferromagnet CeIn3"

<p><strong>Figure 2:</strong> Derivation of the Kondo-Heisenberg model.</p><p><strong>Description:</strong></p><p>The electronic structure of CeIn3 on the reciprocal-space path RGXMG (G=Gamma) is stored in "fbands.dat" and in "allotherbands.dat". The file "fbands.dat" has 15 columns, where the first column provides the wave-vector projection onto the path RGXMG and columns 2-15 the energies of the 14 <i>f</i>-bands. In the file "allotherbands.dat" the first column corresponds to the wave-vector values and the other columns contain all remaining bands.</p><p>The wave-vector dependent interactions are stored in "InteractionSpectrum.dat". Here, the first column provides the wave-vector projection onto the path RGXMG, the second column the RKKY-interaction, the third column the superexchange, the fourth column the particle-particle interaction and the last column the sum of all interactions.</p><p> </p><p><strong>Figure 3:</strong> Calculated and measured magnon dispersion and dynamic magnetic susceptibility in the antiferromagnetic state of CeIn3.</p><p><strong>Description:</strong></p><p>The imaginary part of the dynamic magnetic susceptibility, as inferred from high-energy inelastic neutron scattering intensity, on the reciprocal space-path RG is stored in the file "HighEnergy_Int_RG.dat" in terms of a 59 x 68 matrix. Here, the first index enumerates the wavevector-projection onto the path RG and the second index the energy transfer. The respective wave-vector and energy values are stored in "HighEnergy_Q_RG.dat" and "HighEnergy_E_RG.dat", respectively. Similarly, inelastic neutron scattering intensity, wave-vector values, and energy-transfer values for the paths GX, XM, and MG are stored in the files "HighEnergy_Int_GX.dat", "HighEnergy_Q_GX.dat", "HighEnergy_E_GX.dat", "HighEnergy_Int_XM.dat", "HighEnergy_Q_XM.dat", "HighEnergy_E_XM.dat", "HighEnergy_Int_MG.dat", "HighEnergy_Q_MG.dat", and "HighEnergy_E_MG.dat".</p><p>The imaginary part of the dynamic magnetic susceptibility on the path RGXMG, as inferred from theory, is stored in the files "Theory_Q_RGXMG.dat", "Theory_E_RGXMG.dat", and "Theory_Int_RGXMG.dat", where the first, second, and third file provide the wave-vector projections, the energy transfers, and the values of the dynamic magnetic susceptibility, respectively.</p><p>The dispersion on the path RGXMG inferred from MOPAM calculations is stored in "MOPAM-Dispersion_RGXMG.dat" and the dispersion of the J1-model in "J1Model-Dispersion_RGXMG.dat". In both files, the first column corresponds to the wave-vector projection onto the path RGXMG and the second column to the energy.</p><p>Cuts at the constant wave-vectors Q1 and Q2, as inferred from experiments, are stored in "Experiment_ConstQ1.dat" and "Experiment_ConstQ2.dat", respectively. The cuts from theory are stored in "Theory_ConstQ1.dat" and "Theory_ConstQ2.dat".</p><p>The integral over the dynamic magnetic susceptibility on the path RGXMG inferred from theory is stored in "Theory_IntegralOverchi.dat", where the first and second columns provide the wave-vector projection and the integrated values, respectively. The values inferred from experiment are stored in "Experiment_IntegralOverchi.dat". The first and second columns provide the wave-vector projection and the integrated values, respectively. The last column provides the error bars.</p><p> </p><p><strong>Figure 4: </strong>Signature of long-range RKKY interactions in CeIn3,</p><p><strong>Description:</strong></p><p>High-resolution inelastic neutron scattering data on the path RG are presented in "HighResolution_Int_RG.dat". The first and second index enumerates the wave-vector projection onto the path RG and energy transfer, respectively. The respective values are stored in "HighResolution_Q_RG.dat" and "HighResolution_E_RG.dat".</p><p>Similarly, data for the paths RX and RM are stored in the files "HighResolution_Int_RX.dat", "HighResolution_Q_RX.dat", "HighResolution_E_RX.dat", "HighResolution_Int_RM.dat", "HighResolution_Q_RM.dat", and "HighResolution_E_RM.dat".</p><p>The dispersion inferred from MOPAM calculations on the paths RG, RX, and RM, is stored in "MOPAM-Dispersion_RG.dat", "MOPAM-Dispersion_RX.dat", and "MOPAM-Dispersion_RM.dat", respectively. Similarly, the dispersions of the J1 model on the paths RG, RX, and RM, are stored in "J1Model-Dispersion_RG.dat", "J1Model-Dispersion_RX.dat", and "J1Model-Dispersion_RM.dat", respectively.</p><p>Cuts at constant energies 0.6 meV and 1.4 meV along RG are stored in "HighResolution_RG_ConstEcut_0p6meV.dat" and "HighResolution_RG_ConstEcut_1p4meV.dat", respectively. Similarly, cuts along RX are stored in "HighResolution_RX_ConstEcut_0p6meV.dat" "and HighResolution_RX_ConstEcut_1p4meV.dat" and along RM in "HighResolution_RM_ConstEcut_0p4meV.dat" "and HighResolution_RM_ConstEcut_1p4meV.dat".</p><p> </p&gt