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We investigated the spectrum of density fluctuations of a liquid crystal, CB7CB, in two different orientations by using high-resolution inelastic x-ray scattering. Our analysis, based on Bayesian principles, revealed that high-frequency collective excitations propagate through this mesoscale-ordered sample in a peculiar manner that lies somewhere between those observed in liquids and crystalline systems. Interestingly, when we probed longer length scales, a more pronounced solid-like response emerged. This was mainly characterized by anomalously sharp inelastic excitations and the onset of shear mode propagation. Comparison with previous x-ray diffraction results suggests a correlation between the observed behavior and the mesogen arrangement. [ABSTRACT FROM AUTHOR]

Structural and vibrational properties of aqueous solutions of alkali hydroxides (LiOH, NaOH, and KOH) are computed using quantum molecular dynamics simulations for solute concentrations ranging between 1 and 10M. Element-resolved partial radial distribution functions, neutron and x-ray structure factors, and angular distribution functions are computed for the three hydroxide solutions as a function of concentration. The vibrational spectra and frequency-dependent conductivity are computed from the Fourier transforms of velocity autocorrelation and current autocorrelation functions. Our results for the structure are validated with the available neutron data for 17M concentration of NaOH in water [Semrouni et al., Phys. Chem. Chem. Phys. 21, 6828 (2019)]. We found that the larger ionic radius [ r L i + < r N a + < r K + ] and higher concentration disturb the hydrogen-bond network of water, resulting in more disordered cationic hydration shell. Our ab initio simulation data for solute concentrations ranging between 1 and 10M can be used to guide future elastic and inelastic neutron-scattering experiments. [ABSTRACT FROM AUTHOR]

Vibrational spectroscopy can be said to have started with the seminal work of Coblentz in the 1900s, who recorded the first recognisable infrared spectra. Today, vibrational spectroscopy is ubiquitous and there are many ways to measure a vibrational spectrum. But this is usually only the first step, almost always there is a need to assign the resulting spectra: “what property of the system results in a feature at this energy”? How this question has been answered has changed over the last century, as our understanding of the fundamental physics of matter has evolved. In this Perspective, I will present my view of how the analysis of vibrational spectra has evolved over time. The article is divided into three sections: past, present and future. The “past” section consists of a very brief history of vibrational spectroscopy. The “present” is centered around ab initio studies, particularly with density functional theory (DFT) and I will describe how this has become almost routine. For the “future”, I will extrapolate current trends and also speculate as to what might come next. [ABSTRACT FROM AUTHOR]

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[Display omitted] After several decades of studies of high-temperature superconductivity, there is no compelling theory for the mechanism yet; however, the spin fluctuations have been widely believed to play a crucial role in forming the superconducting Cooper pairs. The recent discovery of high-temperature superconductivity near 80 K in the bilayer nickelate La 3 Ni 2 O 7 under pressure provides a new platform to elucidate the origins of high-temperature superconductivity. We perform elastic and inelastic neutron scattering studies on a polycrystalline sample of La 3 Ni 2 O 7− δ at ambient pressure. No magnetic order can be identified down to 10 K. The absence of long-range magnetic order in neutron diffraction measurements may be ascribed to the smallness of the magnetic moment. However, we observe a weak flat spin-fluctuation signal in the inelastic scattering spectra at ∼ 45 meV. The observed spin excitations could be interpreted as a result of strong interlayer and weak intralayer magnetic couplings for stripe-type antiferromagnetic orders. Our results provide crucial information on the spin dynamics and are thus important for understanding the superconductivity in La 3 Ni 2 O 7. [ABSTRACT FROM AUTHOR]

Recent advances in the study of cobaltites have unveiled their potential as a promising platform for realizing Kitaev physics in honeycomb systems and the Ising model in weakly coupled chain materials. In this manuscript, we explore the magnetic properties of pyroxene SrCoGe2O6 using a combination of neutron scattering, ab initio methods, and linear spin-wave theory. Through careful examination of inelastic neutron scattering powder spectra, we propose a modified Kitaev model to accurately describe the twisted chains of edge-sharing octahedra surrounding Co2+ ions. The extended Kitaev–Heisenberg model, including a significant anisotropic bonddependent exchange term with K /|J| = 0.96, is identified as the key descriptor of the magnetic interactions in SrCoGe2O6. Furthermore, our heat capacity measurements reveal an effect of an external magnetic field (approximately 13 T) which shifts the system from a fragile antiferromagnetic ordering with TN = 9 K to a field-induced state. We argue that pyroxenes, particularly those modified by substituting Ge with Si and its less extended p orbitals, emerge as a platform for the Kitaev model. This opens up possibilities for advancing our understanding of Kitaev physics. [ABSTRACT FROM AUTHOR]

Thiophosgene is one of the principal C=S building blocks in synthetic chemistry. At room temperature, thiophosgene is a red liquid. While its properties in the liquid and gaseous states are well known, a comprehensive characterization of thiophosgene in its solid state is presented here. Differential scanning calorimetry shows that thiophosgene forms a supercooled melt before rapidly crystallizing. Its melting point is 231.85 K (−41.3 °C). At 80 K, thiophosgene crystallizes in space group P63/m [No. 174, a = b = 5.9645 (2), c = 6.2835 (3) Å, V = 193.59 (2) Å3]. The molecule shows a distinct rotational disorder: all S and Cl positions are of mixed occupancy and the disorder does not resolve at temperatures as low as 10 K, as was shown by neutron powder diffraction. Infrared, Raman and inelastic neutron scattering spectra were collected and assigned with the aid of quantum chemical calculations. A larger ordered structural model allowed for better agreement between the measured and calculated spectra, further indicating that disorder is an inherent feature of solid‐state thiophosgene. [ABSTRACT FROM AUTHOR]

We used THz (terahertz) and INS (inelastic neutron scattering) spectroscopies to study the interaction between an endohedral noble gas atom and the C60 molecular cage. The THz absorption spectra of powdered A@C60 samples (A = Ar, Ne, Kr) were measured in the energy range from 0.6 to 75 meV for a series of temperatures between 5 and 300 K. The INS measurements were carried out at liquid helium temperature in the energy transfer range from 0.78 to 54.6 meV. The THz spectra are dominated by one line, between 7 and 12 meV, at low temperatures for three noble gas atoms studied. The line shifts to higher energy and broadens as the temperature is increased. Using a spherical oscillator model, with a temperature-independent parameterized potential function and an atom-displacement-induced dipole moment, we show that the change of the THz spectrum shape with temperature is caused by the anharmonicity of the potential function. We find good agreement between experimentally determined potential energy functions and functions calculated with Lennard-Jones additive pair-wise potentials with parameters taken from the work of Pang and Brisse, J. Chem. Phys. 97, 8562 (1993). [ABSTRACT FROM AUTHOR]

We used THz (terahertz) and INS (inelastic neutron scattering) spectroscopies to study the interaction between an endohedral noble gas atom and the C60 molecular cage. The THz absorption spectra of powdered A@C60 samples (A = Ar, Ne, Kr) were measured in the energy range from 0.6 to 75 meV for a series of temperatures between 5 and 300 K. The INS measurements were carried out at liquid helium temperature in the energy transfer range from 0.78 to 54.6 meV. The THz spectra are dominated by one line, between 7 and 12 meV, at low temperatures for three noble gas atoms studied. The line shifts to higher energy and broadens as the temperature is increased. Using a spherical oscillator model, with a temperature-independent parameterized potential function and an atom-displacement-induced dipole moment, we show that the change of the THz spectrum shape with temperature is caused by the anharmonicity of the potential function. We find good agreement between experimentally determined potential energy functions and functions calculated with Lennard-Jones additive pair-wise potentials with parameters taken from the work of Pang and Brisse, J. Chem. Phys. 97, 8562 (1993). [ABSTRACT FROM AUTHOR]

Halide perovskites emerge as promising candidates for thermoelectrics due to their ultralow thermal conductivity. The conventional theory based on the phonon gas model, which treats thermal transport as particle‐like behavior, shows limitations to describe the unusual thermal transport property in some halide perovskites with strong anharmonicity. Here, the significance of phonon coherence effect on thermal transport of bismuth‐halide perovskite Cs3Bi2Br9 is reported by inelastic neutron scattering and simulations including density functional theory and machine‐learning potential based molecular dynamics. This study shows that the restrictive low‐energy acoustic phonons lead to the limited particle‐like thermal conductivity, which seriously underestimates the lattice thermal conductivity of Cs3Bi2Br9. The significant contribution of wave‐like optical phonon modes, driven by the coherence effect, accounts for an additional ≈50% wave‐like thermal conductivity. Besides, the experimental weak temperature dependence of thermal conductivity along z direction (κ ≈T−0.35) is well reproduced by calculation (κ ≈T−0.37) when including phonon coherence. This work highlights the critical role of phonon coherence in Cs3Bi2Br9 and enhances understanding on the unusual thermal transport properties in halide perovskites and other related materials with strong anharmonicity. [ABSTRACT FROM AUTHOR]

Gamma emission induced by the irradiation of nickel and zirconium with fission neutrons was investigated with the FaNGaS (Fast Neutron–induced Gamma-ray Spectrometry) instrument operated at Heinz Maier-Leibnitz Zentrum. Measurements were done at an angle of 90° with respect to the direction of the fission neutron beam (average neutron energy of 2.18 MeV). We report on the relative intensities and production cross sections of 265 gamma lines (163 for nickel and 102 for zirconium). Consistency with available literature data was evaluated. The cross section of the 90Zr(n,n′)90mZr reaction was determined to be 88 ± 8 mb. For a counting time of 12 h, the detection limits of 0.7 and 1.3 mg were estimated for nickel and zirconium, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the spin wave theory is applied to the Heisenberg spin bilayer with intralayer ferromagnetic interaction J 1 , intralayer single-ion anisotropy D and interlayer antiferromagnetic interaction J 2 . It is found that the effects of both D and J 2 on the thermodynamic quantities give rise to the two different low-temperature asymptotic behaviors with and without exponential law. For D > 0 , the interlayer antiferromagnetic interaction can induce the appearance of the maximum of the layer magnetization at finite temperatures. At the location of the layer magnetization maximum, the approximate behaviors (such as the power, linear, rational, exponential and logarithmic laws) which are driven by the temperature or the anisotropy, are obtained for the low-temperature thermodynamic properties. It is shown that the presence of antiferromagnetic interlayer interaction J 2 clearly induces more quantum fluctuations than the case where the interlayer interaction J 2 is ferromagnetic. Our results of the layer magnetization agree with the experimental data of the layered van der Waals crystal FeCl2 at low temperatures. In the monolayer case of J 2 = 0 , our results are in agreement with the findings obtained by the existing theories and the quantum Monte Carlo data. [ABSTRACT FROM AUTHOR]

The kink structure in band dispersion usually refers to a certain electron-boson interaction, which is crucial in understanding the pairing in unconventional superconductors. Here we report the evidence of the observation of a kink structure in Fe-based superconductor CsCa2Fe4As4F2 using angle-resolved photoemission spectroscopy. The kink shows an orbital selective and momentum dependent behavior, which is located at 15 meV below Fermi level along the Γ − M direction at the band with dxz orbital character and vanishes when approaching the Γ − X direction, correlated with a slight decrease of the superconducting gap. Most importantly, this kink structure disappears when the superconducting gap closes, indicating that the corresponding bosonic mode (~ 9 ± 1 meV) is closely related to superconductivity. However, the origin of this mode remains unidentified, since it cannot be related to phonons or the spin resonance mode (~15 meV) observed by inelastic neutron scattering. The behavior of this mode is rather unique and challenges our present understanding of the superconducting paring mechanism of the bilayer FeAs-based superconductors. The kink structure in the band dispersion can be linked to electron-boson interaction and has been reported in unconventional superconductors. Here the authors observe an orbital selective and momentum dependent kink feature in an Fe-based superconductor, which is highly correlated with superconductivity. [ABSTRACT FROM AUTHOR]

Magnetic frustration is a route for novel ground states, including spin liquids and spin ices. Such frustration can be introduced through either lattice geometry or incompatible exchange interactions. Here, we find that epitaxial strain is an effective tool for tuning antiferromagnetic exchange interactions in a square-lattice system. By studying the magnon excitations in La2NiO4 films using resonant inelastic x-ray scattering, we show that the magnon displays substantial dispersion along the antiferromagnetic zone boundary, at energies that depend on the lattice of the film's substrate. Using first principles simulations and an effective spin model, we demonstrate that the antiferromagnetic next-nearest neighbour coupling is a consequence of the two-orbital nature of La2NiO4. Altogether, we illustrate that compressive epitaxial strain enhances this coupling and, as a result, increases the level of incompatibility between exchange interactions within a model square-lattice system. Frustration in magnetic systems may lead to exotic quantum phases such as spin liquid and spin ice state. Here the authors demonstrate that compressive epitaxial strain in La2NiO4 films deposited on different substrates can tune antiferromagnetic exchange interactions and increase the degree of frustration through the increased level of incompatibility between exchange interactions. [ABSTRACT FROM AUTHOR]

Magnetic frustration is a route for novel ground states, including spin liquids and spin ices. Such frustration can be introduced through either lattice geometry or incompatible exchange interactions. Here, we find that epitaxial strain is an effective tool for tuning antiferromagnetic exchange interactions in a square-lattice system. By studying the magnon excitations in La2NiO4 films using resonant inelastic x-ray scattering, we show that the magnon displays substantial dispersion along the antiferromagnetic zone boundary, at energies that depend on the lattice of the film's substrate. Using first principles simulations and an effective spin model, we demonstrate that the antiferromagnetic next-nearest neighbour coupling is a consequence of the two-orbital nature of La2NiO4. Altogether, we illustrate that compressive epitaxial strain enhances this coupling and, as a result, increases the level of incompatibility between exchange interactions within a model square-lattice system. Frustration in magnetic systems may lead to exotic quantum phases such as spin liquid and spin ice state. Here the authors demonstrate that compressive epitaxial strain in La2NiO4 films deposited on different substrates can tune antiferromagnetic exchange interactions and increase the degree of frustration through the increased level of incompatibility between exchange interactions. [ABSTRACT FROM AUTHOR]

We calculate electronic structure and spin susceptibility dependencies on doping within the framework of a cluster perturbation theory for strongly correlated electronic systems. The change in the susceptibility with increasing doping is qualitatively consistent with the experimental data on resonant inelastic X-ray scattering and inelastic neutron scattering, as well as with the results of the calculations within the quantum Monte Carlo method. [ABSTRACT FROM AUTHOR]

Prompt gamma-ray neutron activation analysis (PGNAA) is a technique that can be used online or in situ to measure the concentrations of different elements in natural materials without altering the elements' chemical forms in matter. The goal of the current work was to use a 2.5 MeV neutron beam to boost the yield of a portable PGNAA (Genie 16) system. Optimizations were performed to reduce the superimposition between gamma rays from the setup's elements and those from heavy metals. The value of the new optimization was verified by the improvement of the minimum detectable concentrations of sulfur, zinc, titanium, nickel, and chrome in soil samples. [ABSTRACT FROM AUTHOR]

Neutron scattering methods such as quasielastic neutron scattering (QENS) and inelastic neutron scattering (INS) have been used to study the reactivity of propene and 1-octene over the acid zeolite catalyst H-ZSM-5. The high activity of the catalyst causes the alkenes to form linear oligomers below room temperature. INS has shown that the reaction proceeds through a hydrogenbonded intermediate. Studies using propane as an inert analogue for propene have found that the adsorbed C3 molecules spend much of their time undergoing short jumps within the pore channels of the zeolite. Hydrothermal dealumination plays an important role in determining the activity of zeolite catalysts. Dealumination was found to delay the onset of catalytic activity for oligomerisation to higher temperatures and increase the mobility of hydrocarbons within the zeolite, both due to reduced acid-hydrocarbon interactions. [ABSTRACT FROM AUTHOR]

Magnetic materials with noncoplanar magnetic structures can show unusual physical properties driven by nontrivial topology. Topologically-active states are often multi-q structures, which are challenging to stabilize in models and to identify in materials. Here, we use inelastic neutron-scattering experiments to show that the insulating double perovskites Ba2YRuO6 and Ba2LuRuO6 host a noncoplanar 3-q structure on the face-centered cubic lattice. Quantitative analysis of our neutron-scattering data reveals that these 3-q states are stabilized by biquadratic interactions. Our study identifies double perovskites as a highly promising class of materials to realize topological magnetism, elucidates the stabilization mechanism of the 3-q state in these materials, and establishes neutron spectroscopy on powder samples as a valuable technique to distinguish multi-q from single-q states, facilitating the discovery of topologically-nontrivial magnetic materials. [ABSTRACT FROM AUTHOR]

We present an experimental investigation of methylammonium lead tribromide single crystals in the orthorhombic, tetragonal, and cubic phases based on inelastic and deep inelastic neutron scattering experiments. We show how the average hydrogen nuclear kinetic energy, mainly affected by zero-point vibrational energies, shows differences larger compared to the changes simply related to temperature effects when moving from one phase to another. In particular, the Gaussian contribution to the average nuclear kinetic energy is larger in the tetragonal phase compared to the cubic and orthorhombic ones. Moreover, we find that the vibrational densities of states of MAPbBr3 single crystals in the orthorhombic phase are compatible with previously reported results on powder samples, and that the only vibrational modes that show slightly different frequencies compared to MAPbI3 are those in the energy range between 100 and 300 cm−1, related to librational/rotational modes. As these shifts are of about 10 cm−1 and do not affect any higher-energy vibrational mode, we conclude that the zero-point energies and average nuclear kinetic energies in the two-hybrid organic/inorganic perovskites are expected to be approximately the same within a harmonic framework. [ABSTRACT FROM AUTHOR]

In this study, a simple and efficient non-covalent functionalization method was developed to introduce conducting polymer of P3HT onto pristine MWCNT and hydroxyl MWCNT surfaces without causing significant changes in electrical characteristics, especially if used as a sensing material. Electron microscopy (FE-SEM) and (HR-TEM) were used to examine the surface morphology of nanocomposites, which demonstrated that the MWCNTs were well wrapped by P3HT. EDX analysis showed interactions between MWCNT-OH and P3HT, with a higher sulfur content of 7.77 wt% from P3HT. Additionally, the diameters of both pristine MWCNT (24.46 nm) and MWCNT-OH (27.56 nm) increased significantly when they form nanocomposites (35.35 nm and 39.40 nm respectively). Further characterization of the produced P3HT-MWCNT nanocomposite was performed using FT-IR and Raman spectroscopy. It was discovered that MWCNTs were dispersed uniformly, with a substantial interaction between P3HT and MWCNTs. The introduction of malathion on the surface of the nanocomposites reveals interaction between P3HT and malathion via intermolecular hydrogen bonding of thiophene, as evidenced by inelastic neutron scattering (INS) spectroscopy, suggesting that the P3HT/MWCNT has the potential as a promising sensing material for organophosphate compounds detection.

We use elastic and inelastic neutron scattering (INS) to study the antiferromagnetic (AF) phase transitions and spin excitations in the two-dimensional (2D) zig-zag antiferromagnet FePSe3. By determining the magnetic order parameter across the AF phase transition, we conclude that the AF phase transition in FePSe3 is first-order in nature. In addition, our INS measurements reveal that the spin waves in the AF ordered state have a large easy-axis magnetic anisotropy gap, consistent with an Ising Hamiltonian, and possible biquadratic magnetic exchange interactions. On warming across TN, we find that dispersive spin excitations associated with three-fold rotational symmetric AF fluctuations change into FM spin fluctuations above TN. These results suggest that the first-order AF phase transition in FePSe3 may arise from the competition between C3 symmetric AF and C1 symmetric FM spin fluctuations around TN, in place of a conventional second-order AF phase transition. [ABSTRACT FROM AUTHOR]

Vibrational spectroscopy allows us to understand complex physical and chemical interactions of molecular crystals and liquids such as ammonia, which has recently emerged as a strong hydrogen fuel candidate to support a sustainable society. We report inelastic neutron scattering measurement of vibrational properties of ammonia along the solid-to-liquid phase transition with high enough resolution for direct comparisons to ab-initio simulations. Theoretical analysis reveals the essential role of nuclear quantum effects (NQEs) for correctly describing the intermolecular spectrum as well as high energy intramolecular N-H stretching modes. This is achieved by training neural network models using ab-initio path-integral molecular dynamics (PIMD) simulations, thereby encompassing large spatiotemporal trajectories required to resolve low energy dynamics while retaining NQEs. Our results not only establish the role of NQEs in ammonia but also provide general computational frameworks to study complex molecular systems with NQEs. Through neutron scattering experiments coupled with machine learning, the authors uncover the strong role of nuclear quantum effects in the dynamics of ammonia in both its solid and technologically relevant liquid phase. [ABSTRACT FROM AUTHOR]

This work proposes a monostable symmetric piezoelectric energy harvester based on the cantilever structure and magnetic excitation action (M-PEH). The governing equations of M-PEH are derived based on its kinematic properties. The intrinsic frequency of the piezoelectric cantilever beam was obtained by modal simulation. It has been demonstrated that the mode of arrangement of the magnetic poles has a significant effect on the output voltage of the energy harvester. The proposed M-PEH has four driving magnets with a mass of 6 g and a radial driving distance of 15 mm for more efficient energy harvesting. The experimental results show that the maximum voltage of the M-PEH with the double U-type rotor was 31.2 V at 240 rpm and 110 kΩ external resistance. The average power of the PEH with the double U-type rotor was 16.562 mW at a speed of 240 rpm with an outer resistance of 20 kΩ. The energy harvester with a double U-type rotor can realize a voltage output of not less than 10 V in the range of 60–300 rpm when the same poles of the tip magnets are arranged outward. The M-PEH can also easily light up LEDs or miniature electronic watches with speeds of 120 rpm and 240 rpm. This further proves that the proposed piezoelectric energy harvester (M-PEH) has a better energy harvesting effect and great potential for practical applications. [ABSTRACT FROM AUTHOR]

The potential of prompt gamma analysis based on inelastic scattering of 2.5 MeV neutrons for a rapid characterization of NdFeB permanent magnets is investigated by means of numerical simulations using an HPGe detector and a CZT detector-array. The results show that rapid assay of a 42 g magnet can be achieved in some minutes when the neutron flux at sample position is about 1.6 × 109 cm−2 s−1 and the detector count rate limited to 500 kcps. Such a high neutron flux could be delivered by a compact 5 MeV proton accelerator with a thick beryllium target for neutron production through the 9Be(p,xn)9Be. [ABSTRACT FROM AUTHOR]

Dynamic neutron scattering probes unique nanoscale dynamics via measurement of energy exchanged between a sample and the neutrons. The two spectrometers that investigate processes with characteristic times around a nanosecond are backscattering (BS) and neutron spin-echo (NSE). We present a new method for measuring dynamics using an oscillating cosine-like energy-distribution neutron-package at the sample and measure solely the portion scattered into the elastic line. This portion corresponds to elastically scattered neutrons and, in addition, inelastic components that are scattered with a probability directly proportional to the cosine Fourier-coefficients of the exchanged-energy spectrum. The counts at the detector thus correspond to the van Hove intermediate scattering function. We denote this new method as "Fourier transform neutron scattering" (FTNS), it being broadly analogous to IR and Raman spectroscopies. Here, the realization of such a concept is investigated using an oscillating incident beam produced via a precession method and a secondary spectrometer identical to a BS instrument using crystal analyzers. The instrument is denoted "Modulated Intensity with Diffraction Analysis Spectrometer" (MIDAS). However, simpler approaches, e.g., choppers, may also be used for an FTNS instrument. The theory behind MIDAS is presented, supported by numerical calculations and in silico experiments. Finally, we present a Monte Carlo simulation to compare BS and MIDAS spectrometers. This shows that MIDAS has almost 100 times more incident flux than standard BS, but due to the better signal-to-noise ratio of BS, the final information acquisition rate gain of MIDAS is approximately a factor of 2. [ABSTRACT FROM AUTHOR]

In this work, an inelastic neutron scattering system was developed for element analysis in limestone with a D–T neutron generator and a 3*3 inch LaBr3 detector. Six sets of simulated limestone samples were prepared by proportionally mixing high-purity CaCO3, SiO2, and MgO powders and measured in situ with Inelastic Neutron Scattering (INS) facility. Empirical mode decomposition (EMD) technique is used for noise reduction and filtering of the original gamma energy spectrum. The energy window method was used for quantitative analysis. The minimum detection limits for Ca, Si, and Mg in the samples were determined to be 0.019%, 0.021%, and 0.026%, respectively. The linear relationship between elemental content and the gamma-ray counts has been studied. [ABSTRACT FROM AUTHOR]

Magnon spin currents in the ferrimagnetic garnet Tb3Fe5O12 with 4f electrons were examined through the spin-Seebeck effect and neutron scattering measurements. The compound shows a magnetic compensation, where the spin-Seebeck signal reverses above and below T comp = 249.5 (4) K. Unpolarized neutron scattering unveils two major magnon branches with finite energy gaps, which are well explained in the framework of spin-wave theory. Their temperature dependencies and the direction of the precession motion of magnetic moments, i.e., magnon polarization, defined using polarized neutrons, explain the reversal at T comp and decay of the spin-Seebeck signals at low temperatures. We illustrate an example that momentum- and energy-resolved microscopic information is a prerequisite to understand the magnon spin current. [ABSTRACT FROM AUTHOR]

Magnon spin currents in the ferrimagnetic garnet Tb3Fe5O12 with 4f electrons were examined through the spin-Seebeck effect and neutron scattering measurements. The compound shows a magnetic compensation, where the spin-Seebeck signal reverses above and below T comp = 249.5 (4) K. Unpolarized neutron scattering unveils two major magnon branches with finite energy gaps, which are well explained in the framework of spin-wave theory. Their temperature dependencies and the direction of the precession motion of magnetic moments, i.e., magnon polarization, defined using polarized neutrons, explain the reversal at T comp and decay of the spin-Seebeck signals at low temperatures. We illustrate an example that momentum- and energy-resolved microscopic information is a prerequisite to understand the magnon spin current. [ABSTRACT FROM AUTHOR]

Magnetism of molecular quantum materials such as single-molecule magnets (SMMs) has been actively studied for potential applications in the new generation of high-density data storage using SMMs and quantum information science. Magnetic anisotropy and spin–phonon coupling are two key properties of d- and f-metal complexes. Here, phonons refer to both intermolecular and intramolecular vibrations. Direct determination of magnetic anisotropy and experimental studies of spin–phonon coupling are critical to the understanding of molecular magnetism. This article discusses our recent approach in using three complementary techniques, far-IR and Raman magneto-spectroscopies (FIRMS and RaMS, respectively) and inelastic neutron scatterings (INS), to determine magnetic excited states. Spin–phonon couplings are observed in FIRMS and RaMS. DFT phonon calculations give energies and symmetries of phonons as well as calculated INS spectra which help identify magnetic peaks in experimental INS spectra. [ABSTRACT FROM AUTHOR]

The interplay of charge, spin, lattice, and orbital degrees of freedom in correlated materials often leads to rich and exotic properties. Recent studies have brought new perspectives to bosonic collective excitations in correlated materials. For example, inelastic neutron scattering experiments revealed non-trivial band topology for magnons and spin--orbit excitons (SOEs) in a quantum magnet CoTiO3 (CTO). Here, we report phonon properties resulting from a combination of strong spin--orbit coupling, large crystal field splitting, and trigonal distortion in CTO. Specifically, the interaction between SOEs and phonons endows chirality to two Eg phonon modes and leads to large phonon magnetic moments observed in magneto-Raman spectra. The remarkably strong magneto-phononic effect originates from the hybridization of SOEs and phonons due to their close energy proximity. While chiral phonons have been associated with electronic topology in some materials, our work suggests opportunities may arise by exploring chiral phonons coupled to topological bosons. [ABSTRACT FROM AUTHOR]

The magnon excitation by ultrasound injection in Y3Fe5O12 is studied by inelastic neutron scattering. Both longitudinal and transverse ultrasound injections enhanced the inelastic neutron scattering intensity. We analyzed the nonequilibrium magnon steady state using the effective magnon temperature model. The large deviation of the effective magnon temperature from the sample temperature is observed at the ultrasound longitudinal mode along [0, 0, 1] at ∼10 K and [1, 1, 1] at ∼140 K. This dependence suggests that the nonequilibrium steady state can be achieved only by strong spin–lattice coupling in Y3Fe5O12. The spin–lattice coupling exhibits a decrease largely above 100 K, indicating that it could be the main origin of the degradation of longitudinal spin Seebeck effect at the temperature range. [ABSTRACT FROM AUTHOR]

Knowledge about nonequilibrium dynamics in spin systems is of great importance to both fundamental science and technological applications. Inelastic neutron scattering (INS) is an indispensable tool to study spin excitations in complex magnetic materials. However, conventional INS spectrometers currently only perform steady-state measurements and probe averaged properties over many collision events between spin excitations in thermodynamic equilibrium, while the exact picture of re-equilibration of these excitations remains unknown. In this paper, we report on the design and implementation of a time-resolved laser–neutron pump–probe capability at hybrid spectrometer (beamline 14-B) at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. This capability allows us to excite out-of-equilibrium magnons with a nanosecond pulsed laser source and probe the resulting dynamics using INS. Here, we discussed technical aspects to implement such a capability in a neutron beamline, including choices of suitable neutron instrumentation and material systems, laser excitation scheme, experimental configurations, and relevant firmware and software development to allow for time-synchronized pump–probe measurements. We demonstrated that the laser-induced nonequilibrium structure factor is able to be resolved by INS in a quantum magnet. The method developed in this work will provide SNS with advanced capabilities for performing out-of-equilibrium measurements, opening up an entirely new research direction to study out-of-equilibrium phenomena using neutrons. [ABSTRACT FROM AUTHOR]

The desire for intrinsically low lattice thermal conductivity (κL) in thermoelectrics motivates numerous efforts on understanding the microscopic mechanisms of heat transport in solids. Here, based on theoretical calculations, we demonstrate that α-MgAgSb hosts low-energy localized phonon bands and avoided crossing of the rattler modes, which coincides with the inelastic neutron scattering result. Using the two-channel lattice dynamical approach, we find, besides the conventional contribution (∼70% at 300 K) from particlelike phonons propagating, the coherence contribution dominated by the wavelike tunneling of phonons accounts for ∼30% of the total κL at 300 K. By considering dual contributions, our calculated room-temperature κL of 0.64 W m−1 K−1 well agrees with the experimental value of 0.63 W m−1 K−1. More importantly, our computations give a nonstandard κL ∝ T−0.61 dependence, perfectly explaining the abnormal temperature-trend of ∼T−0.57 in experiment for α-MgAgSb. By molecular dynamics simulation, we reveal that the structure simultaneously has soft crystalline sublattices with the metavalent bonding and fluctuating liquid-like sublattices with thermally induced large amplitude vibrations. These diverse forms of chemical bonding arouse mixed part-crystal part-liquid state, scatter strongly heat-carrying phonons, and finally produce extremely low κL. The fundamental research from this study will accelerate the design of ultralow-κL materials for energy-conversion applications. [ABSTRACT FROM AUTHOR]

Prompt gamma rays of terbium emitted after (n,nʹγ) inelastic scattering reactions induced by irradiation of a terbium(III) hexahydrate (TbCl3·6H2O) sample with a beam of fission neutrons were investigated with the instrument FaNGaS (Fast Neutron-induced Gamma-ray Spectrometry) at an angle of 90° between neutron beam and detector. At sample position, the fast-neutron flux was 1.13 × 108 cm−2 s−1 and the neutron beam has an average energy of 2.30 MeV. We identified 124 prompt gamma lines from the 159Tb(n,nʹγ)159Tb reaction. Presence of prompt gamma rays from oxygen and chlorine was used for a concise verification of recently published results. Relative gamma-ray intensities, effective cross sections and fast-neutron spectrum-averaged partial production cross sections of the gamma lines are given including comparisons with available literature data. We found a reasonable agreement and the multitude of unreported lines adds decisive value to nuclear spectroscopy. Additionally, we estimated the detection limit of terbium as 1 mg for a counting time of 12 h. [ABSTRACT FROM AUTHOR]

The document titled "Emerging materials in antiferromagnetic spintronics" provides a comprehensive overview of the physics and potential applications of compensated magnets, including antiferromagnets, altermagnets, ferrimagnets, and synthetic antiferromagnets. It is divided into seven thematic groups, covering topics such as topology, spin torques, magnonics, and imaging techniques. The document discusses the latest material developments and offers insights into the fundamental physics of compensated magnets. It also includes articles and perspectives on various topics related to antiferromagnetic materials, such as imaging techniques, ultrafast optics, and the potential of ferrimagnets and synthetic antiferromagnets for hosting topological magnetic textures. The collection provides a valuable resource for researchers interested in the advancements in the field of antiferromagnetic materials. [Extracted from the article]

We present a methodology that, for the first time, allows rigorous quantum calculation of the inelastic neutron scattering (INS) spectra of a triatomic molecule in a nanoscale cavity, in this case, H2O inside the fullerene C60. Both moieties are taken to be rigid. Our treatment incorporates the quantum six-dimensional translation–rotation (TR) wave functions of the encapsulated H2O, which serve as the spatial parts of the initial and final states of the INS transitions. As a result, the simulated INS spectra reflect the coupled TR dynamics of the nanoconfined guest molecule. They also exhibit the features arising from symmetry breaking observed for solid H2O@C60 at low temperatures. Utilizing this methodology, we compute the INS spectra of H2O@C60 for two incident neutron wavelengths and compare them with the corresponding experimental spectra. Good overall agreement is found, and the calculated spectra provide valuable additional insights. [ABSTRACT FROM AUTHOR]

We report the temperature evolution of hydrogen bond (HB) chains and rings in Mn 5 [ ( PO 4 ) 2 ( PO 3 (OH)) 2 ] (HOH) 4 to reveal conduction pathways based on difference Fourier maps with neutron- and synchrotron x-ray diffraction data. Localized proton dynamics for the five distinct hydrogen sites were observed and identified in this study. Their temperature evaluation over ten orders of magnitude in time was followed by means of quasielastic neutron scattering, dielectric spectroscopy, and ab initio molecular dynamics. Two out of the five hydrogen sites are geometrically isolated and are not suitable for long-range proton conduction. Nevertheless, the detected dc conductivity points to long-range charge transport at elevated temperatures, which occurs most likely (1) over H4–H4 sites between semihelical HB chains (interchain-exchanges) and (2) by rotations of O1–H1 and site-exchanging H4–O10–O5 groups along each semihelical HB chain (intrachain-exchanges). The latter dynamics freeze into a proton-glass state at low temperatures. Rotational and site-exchanging motions of HOH and OH ligands seem to be facilitated by collective motions of framework polyhedra, which we detected by inelastic neutron scattering. [ABSTRACT FROM AUTHOR]

Magnetic kagome metals are a promising platform to develop unique quantum transport and optical phenomena caused by the interplay between topological electronic bands, strong correlations, and magnetic order. This interplay may result in exotic quasiparticles that describe the coupled electronic and spin excitations on the frustrated kagome lattice. Here, we observe novel elementary magnetic excitations within the ferromagnetic Mn kagome layers in TbMn6Sn6 using inelastic neutron scattering. We observe sharp, collective acoustic magnons and identify flat-band magnons that are localized to a hexagonal plaquette due to the special geometry of the kagome layer. Surprisingly, we observe another type of elementary magnetic excitation; a chiral magnetic quasiparticle that is also localized on a hexagonal plaquette. The short lifetime of localized flat-band and chiral quasiparticles suggest that they are hybrid excitations that decay into electronic states. S. X. M. Riberolles et al. study the kagome Chern insulator TbMn6Sn6 via inelastic neutron scattering. They observe signatures of chiral and flat-band magnons, which are highly localized in real space and strongly damped in the time domain. [ABSTRACT FROM AUTHOR]

The utilization of polarized neutrons is of great importance in scientific disciplines spanning materials science, physics, biology, and chemistry. However, state-of-the-art multilayer polarizing neutron optics have limitations, particularly low specular reflectivity and polarization at higher scattering vectors/angles, and the requirement of high external magnetic fields to saturate the polarizer magnetization. Here, we show that, by incorporating 11B4C into Fe/Si multilayers, amorphization and smooth interfaces can be achieved, yielding higher neutron reflectivity, less diffuse scattering, and higher polarization. Magnetic coercivity is eliminated, and magnetic saturation can be reached at low external fields (>2 militesla). This approach offers prospects for substantial improvement in polarizing neutron optics with nonintrusive positioning of the polarizer, enhanced flux, increased data accuracy, and further polarizing/analyzing methods at neutron scattering facilities. [ABSTRACT FROM AUTHOR]

Molecular Dynamics simulations study material structure and dynamics at the atomic level. X-ray and neutron scattering experiments probe exactly the same time- and length scales as the simulations. In order to benchmark simulations against measured scattering data, a program is required that computes scattering patterns from simulations with good single-core performance and support for parallelization. In this work, the existing program Sassena is used as a potent solution to this requirement for a range of scattering methods, covering pico- to nanosecond dynamics, as well as the structure from some Ångströms to hundreds of nanometers. In the case of nanometer-level structures, the finite size of the simulation box, which is referred to as the finite size effect, has to be factored into the computations for which a method is described and implemented into Sassena. Additionally, the single-core and parallelization performance of Sassena is investigated, and several improvements are introduced. [ABSTRACT FROM AUTHOR]

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Vanadium-based solid solution alloys potentially serve as safe, high-capacity hydrogen storage materials. Low-vanadium-concentration alloys have low durability, and their hydrogen absorption and desorption amounts decrease by 20 % after 100 cycles. In this study, we conducted reverse Monte Carlo modeling on X-ray diffraction patterns and neutron pair distribution functions of the hydrogen-absorbed and desorbed samples of a V 0.10 Ti 0.36 Cr 0.54 alloy to analyze the variations in the local structure. The local structure surrounding the hydrogen atom in the hydrogen-absorbed phase exhibited minimal changes. In contrast, hydrogen occupied both tetrahedral and octahedral sites of the hydrogen-desorbed phase almost equally during the early cycles; however, the amount of hydrogen occupying the tetrahedral sites increased with the number of cycles. It is speculated that hydrogen absorption and desorption cycling induced grain refinement and/or introduced dislocations, which altered both the amount of hydrogen and the sites occupied in the desorbed phase, thereby decreasing the hydrogen storage capacity. [Display omitted] • Degradation mechanism of V–Ti–Cr hydrogen storage alloy revealed by local structure. • Decrease in hydrogen storage consistent with PDF refinements and p – c isotherms. • Cr–H and Ti–H correlations reproduced by a large atomic ensemble in RMC modeling. • Change in hydrogen occupation positions supplemented by inelastic neutron scattering. [ABSTRACT FROM AUTHOR]

A Timepix3 detector with a 300   μ m silicon sensor has been studied as a novel radiation monitor for the mixed radiation field at the Large Hadron Collider at CERN. This work describes a test campaign carried out at Centro Nacional de Aceleradores with quasi-mono energetic protons (alphas) from 0.6 (1) to 5 (5.6) MeV, where orthogonal irradiations are used to obtain an energy calibration, and a low-energy angular scan to estimate the front dead layer thickness of the sensor. The detector is operated in hole collection mode and at a partial bias of 250   μ m at 50 V , which increases the charge sharing among pixels to mitigate the signal saturation at high energy depositions. The data, supported by FLUKA Monte Carlo simulations of energy losses in the sensor, show that the Timepix3 monitor operates in a linear regime up to energy depositions of around 600 k e V per pixel and 2 M e V per cluster. As a result, the detector has been found to be suitable for measuring charged particle fluxes in the LHC mixed radiation field within the linear calibration regime, with the partial exception of inelastic nuclear reaction hits (mostly from neutrons). [ABSTRACT FROM AUTHOR]

The investigation of supported metal nanoparticle in the presence of H2 is fundamental to better understand their behavior as hydrogenation catalysts. In this respect, this review will focus on the main recent results obtained by Inelastic Neutron Scattering (INS) spectroscopy, which is of particular interest thanks to its ability to provide very detailed vibrational spectra of the H‐containing species in the sample. The review will cover the main results concerning the characterization of the H‐species already present in the pristine catalyst, with a particular focus on carbon‐based materials and their modification upon the interaction with metal nanoparticles. Successively, the forms in which H2 interacts with the catalysts will be examined, starting from H2 physisorption, to then pass to the metal hydride species formed through the splitting of dihydrogen upon the active metallic phase, and finally to the migration of atomic hydrogen from the metal nanoparticles onto the support as a result of hydrogen spillover. The aim of the review is to present an overview of all the hydrogenous species identifiable by INS spectroscopy in hydrogenation catalysts, focusing on the specific case of supported metal nanoparticles systems. [ABSTRACT FROM AUTHOR]

Energy transferred in atom‐surface collisions typically depends strongly on projectile mass, an effect that can be experimentally detected by isotopic substitution. In this work, we present measurements of inelastic H and D atom scattering from a semiconducting Ge(111)c(2×8) surface exhibiting two scattering channels. The first channel shows the expected isotope effect and is quantitatively reproduced by electronically adiabatic molecular dynamics simulations. The second channel involves electronic excitations of the solid and, surprisingly, exhibits almost no isotope effect. We attribute these observations to scattering dynamics, wherein the likelihood of electronic excitation varies with the impact site engaged in the interaction. Key Points: Previous work revealed that H atoms with sufficient translational energy can excite electrons over the band gap of a semiconductor in a surface collision.We studied the isotope effect of the energy transfer by H/D substitution and performed band structure calculations to elucidate the underlying excitation mechanism.Our results suggest a site‐specific mechanism that requires the atom to hit a specific surface site to excite an electron‐hole pair. [ABSTRACT FROM AUTHOR]