To reveal the structure-property relationship in quasi-one-dimensional (1D) spin-chain system Ca_3ZnMnO_6, we present comprehensive results, combining basic physical characterizations such as muon spin relaxation/rotation (μSR), neutron powder diffraction (NPD), inelastic neutron scattering (INS), and theoretical calculations. Ca_3ZnMnO_6 features a dominant intrachain coupling J_1 and two distinct interchain interactions J_2 and J_3, and it undergoes antiferromagnetic ordering below T_N=25 K, as revealed by dc magnetic susceptibility and specific-heat measurements. Zero-field μSR shows persistent spin dynamics below T_N, suggesting unconventional magnetic excitations in the ordered state. NPD results indicate a commensurate magnetic ground state with a propagation vector 𝐤=0, where the Mn spins lie in the ab-plane. INS spectra display dispersive magnetic excitations extending up to about 5 meV, with an energy gap smaller than 0.5 meV. Notably, these spectra exhibit three-dimensional (3D) gapped features rather than the expected 1D behavior, yet spin-wave dispersion analysis confirms an underlying quasi-1D energy hierarchy. We discuss this apparent paradox of 3D-like magnetic excitations in a quasi-1D system in terms of the energy hierarchy modified by nonmagnetic-ion substitution and finite-temperature first-principles calculations. We also suggest that Ca_3ZnMnO_6 could be a potential candidate for an M-type altermagnet.

Skyrmions are particlelike vortices of magnetization with nontrivial topology, which are usually stabilized by Dzyaloshinskii-Moriya interactions (DMI) in noncentrosymmetric bulk materials. Exceptions are centrosymmetric Gd- and Eu-based skyrmion-lattice (SL) hosts with zero DMI, where both the SL stabilization mechanisms and magnetic ground states remain controversial. We address these here by investigating both the static and dynamical spin properties of the centrosymmetric SL host Gd2PdSi3 using muon spectroscopy. We find that spin fluctuations in the noncoplanar SL phase are highly anisotropic, implying that spin anisotropy plays a prominent role in stabilizing this phase. We also observe strongly anisotropic spin dynamics in the ground-state (IC-1) incommensurate magnetic phase of the material, indicating that it hosts a meronlike multi-q structure. In contrast, the higher-field, coplanar IC-2 phase is found to be single q with nearly isotropic spin dynamics.

In this paper, mechanisms for hydration-induced protein mobility changes at high and low temperatures are proposed.

Dental resin composites consist mainly of (di)methacrylate resins and an inorganic filler, and their polymerization reaction is initiated by light activation. Over the years, the physical properties of these light-curing materials have improved, and currently, the polymerization kinetics are well established. However, the influence of hydrogen bond formation and the restriction of molecular mobility during polymer network development is not fully elucidated. Here, we were able to explore the dynamics of hydrogen-rich species in a light-cured model unfilled resin and in a resin-modified polyalkenoate cement by means of a unique combination of light-activation and quasielastic neutron spectroscopy, which was used for modelling of the elastic incoherent structure factor (EISF). This experimental study not only confirms a substantial reduction in the nanoscale mobility of the monomers under light activation but also describes changes to the materials' local structure. In brief, data from both light-cured samples (resin and cement) are described in terms of lone isotropic rotations, indicating that on a time average, the molecules have no preferred orientation. However, before light activation, more complex dynamical descriptions, including conformational jumps, were required to explain the nanoscale mobility of the unpolymerized materials. Clearly, the obtained emerging details on the evolution of the nanostructure in lightcured dental materials open possibilities for further advanced research in the field.

Strong confinement of hydrogen is important for adsorption-based hydrogen storage solutions, which are vital for the transition toward a hydrogen-based economy. The dynamics of hydrogen adsorbed in high-porosity TiC-derived carbon with relatively well-stacked graphenic layers for a carbide-derived carbon is investigated with in situ inelastic and quasi-elastic neutron scattering methods. Both the para-ortho rotational transition and elastic incoherent scattering factor are investigated. Hydrogen is translationally bound at temperatures of 20-80 K. At temperatures of 50 and 80 K, the adsorbed hydrogen exhibits localized jumps over 3.4 and 3.7 Å, respectively, along or between the ultramicropore walls. The restricted jumps of hydrogen in ultramicropores show the confining influence of specific adsorption sites present in the micropores of carbon materials, which limit hydrogen mobility and localize the hydrogen molecules within these pores. These findings yield new insights into the influence of hydrogen loading and temperature on the confinement of hydrogen and the development of carbonaceous adsorbents for high-density hydrogen storage.

Characterization of biopolymers in both dry and weakly hydrated amorphous states has implications for the pharmaceutical industry since it provides understanding of the effect of lyophilisation on stability and biological activity. Atomistic Molecular Dynamics (MD) simulations probe structural and dynamical features related to system functionality. However, while simulations in homogenous aqueous environments are routine, dehydrated model assemblies are a challenge with systems investigated in-silico needing careful consideration; simulated systems potentially differing markedly despite seemingly negligible changes in procedure. Here we propose an in-silico protocol to model proteins in lyophilised and weakly hydrated amorphous states that is both more experimentally representative and routinely applicable. Since the outputs from MD align directly with those accessed by neutron scattering, the efficacy of the simulation protocol proposed is shown by validating against experimental neutron data for apoferritin and insulin. This work also highlights that without cooperative experimental and simulative data, development of simulative procedures using MD alone would prove most challenging. Understanding the stability and activity of freeze-dried bio-macromolecules at low degrees of hydration is crucial for pharmaceutical and food industries, however, the building of in silico models for dynamical studies at a molecular level needs careful consideration. Here, the authors propose a modelling protocol that mimics experimental protein lyophilization, and proteins in weakly hydrated amorphous states, and validate it against experimental neutron scattering data.

We probe the magnetic field -induced Tomonaga-Luttinger liquid (TLL) state in the bond -alternating spin1/2 antiferromagnetic (AFM) chain compound NaVOPO4 using thermodynamic as well as local mu SR and P-31 NMR probes down to mK temperatures in magnetic fields up to 14 T. The mu SR and NMR relaxation rates in the gapless TLL regime decay slowly following characteristic power -law behavior, enabling us to directly determine the interaction parameter K as a function of the magnetic field. These estimates are crosschecked using magnetization and specific heat data. The field -dependent K lies in the range of 0.4 < K < 1 and indicates the repulsive nature of interactions between the spinless fermions, in line with the theoretical predictions. This renders NaVOPO4 the first experimental realization of TLL with repulsive fermionic interactions in hitherto studied S = 1/2 bond -alternating AFM-AFM chain compounds.

Understanding the processes guiding the confinement of adsorbed H-2 in different porous structures is vital for the development of adsorbents for effective cryo-adsorptive H-2 storage systems. Quasi-elastic neutron scattering (QENS) is applied over a wide range of timescales (0.2 ps - 150 ps) to determine different self-diffusion mechanisms of H-2 adsorbed in a carbide (synthesized from TiC via the sol-gel method) derived carbon (sol-gel TiC-CDC) adsorbent with hierarchical porous structure. The bulk and porous structure is characterized by gas adsorption, Raman spectroscopy, and wide-angle X-ray scattering methods. Sol-gel TiC-CDC belongs to a series of CDCs that have been previously characterized and where the self-diffusion of adsorbed H-2 has been investigated with QENS. Sol-gel TiC-CDC is very mesoporous, has relatively high stacking (2.76 graphenic layers per stack), and small interlayer spacing of graphenic sheets (3.43 angstrom) in comparison to other CDCs in the series, thus, being a well-ordered highly porous CDC. Restricted rotational self-diffusion of adsorbed H-2 is determined in ultramicropores (pore width, w, < 7 angstrom) and translationally self-diffusing H-2 adsorbed in multilayers across multiple timescales are determined in micro- and mesopores (7 angstrom< w < 500 angstrom). The microporous and graphenic structure of the CDC does not remarkably affect the self-diffusion of H-2 at high surface coverages. The simultaneous determination of adsorbed H-2 motions across different timescales allows to analyze the influence of micro- and mesopores under H-2 loading conditions, which are close to the ones used in technical applications and are vital for adsorbent optimization.

The layered triangular lattice owing to $1:2$ order of $B$ and ${B}^{\ensuremath{'}}$ sites in the triple perovskite ${A}_{3}B{B}_{2}^{\ensuremath{'}}{\mathrm{O}}_{9}$ family provides an enticing domain for exploring the complex phenomena of quantum spin liquids (QSLs). We report a comprehensive investigation of the ground-state properties of ${\mathrm{Sr}}_{3}{\mathrm{CuTa}}_{2}{\mathrm{O}}_{9}$ that belongs to the above family by employing magnetization, specific heat, and muon spin relaxation $(\ensuremath{\mu}\mathrm{SR})$ experiments down to the lowest temperature of 0.1 K. Analysis of the magnetic susceptibility indicates that the spin lattice is a nearly isotropic $S=1/2$ triangular lattice. We illustrate the observation of a gapless QSL in which conventional spin ordering or freezing effects are absent, even at temperatures more than two orders of magnitude smaller than the exchange energy $({J}_{\mathrm{CW}}/{k}_{\mathrm{B}}\ensuremath{\simeq}\ensuremath{-}5.04 \mathrm{K})$. Magnetic specific heat in zero field follows a power law, ${C}_{\mathrm{m}}\ensuremath{\sim}{T}^{\ensuremath{\eta}}$, below 1.2 K with $\ensuremath{\eta}\ensuremath{\approx}2/3$, which is consistent with a theoretical proposal of the presence of a spinon Fermi surface. Below 1.2 K, the $\ensuremath{\mu}\mathrm{SR}$ relaxation rate shows no temperature dependence, suggesting persistent spin dynamics, as expected for a QSL state. Delving deeper, we also analyze longitudinal field $\ensuremath{\mu}\mathrm{SR}$ spectra, revealing strong dynamical correlations in the spin-disordered ground state. All of these highlight the characteristics of spin entanglement in the QSL state.

p-boronophenylalanine (BPA) is so far the most promising drug in clinical boron neutron capture therapy (BNCT) due to its safety and selective targeting of numerous cancer cells through amino acid transporters, such as LAT1. However, the therapeutic effectiveness of BPA is limited to its low water solubility and poor accumulation in tumor tissues caused by antiport mechanism. Herein, we take advantage of BPA ability to form boronate ester complexes with diols and we report on the coupling of BPA to phase-change ultrasound contrast agents, namely superheated decafluorobutane nanodroplets (NDs) stabilized by a crosslinked shell of poly(vinyl-alcohol) (PVA). The NDs will serve, from one side, to boost the targeting of the cancer cells by enhancing the cellular uptake of BPA through LAT1-mediated endocytosis and by slowing the untoward efflux. From the other side, the high linear energy transfer (LET) particles emitted as a result of nuclear reaction between 10-boron and thermal neutrons will induce the liquid-to-gas transition of the NDs core converting them into echogenic microbubbles detectable by ultrasound imaging (US). The evaluation of US contrast enhancement will allow for in-situ radiation dosimetry. This study demonstrates the effective functionalization of BPA to the NDs and their interactions with the cells and reports on the early-stage in vitro proof-of-concept of neutron-induced NDs-BPA vaporization. The suggested facile technique offers in perspective an innovative approach for both drug delivery and real-time radiation dosimetry with US imaging.

The layered triangular lattice owing to 1 : 2 order of B and B' sites in the triple perovskite A(3)BB'O-2(9) family provides an enticing domain for exploring the complex phenomena of quantum spin liquids (QSLs). We report a comprehensive investigation of the ground-state properties of Sr3CuTa2O9 that belongs to the above family by employing magnetization, specific heat, and muon spin relaxation (mu SR) experiments down to the lowest temperature of 0.1 K. Analysis of the magnetic susceptibility indicates that the spin lattice is a nearly isotropic S = 1/2 triangular lattice. We illustrate the observation of a gapless QSL in which conventional spin ordering or freezing effects are absent, even at temperatures more than two orders of magnitude smaller than the exchange energy (J(CW)/k(B) similar or equal to -5.04 K). Magnetic specific heat in zero field follows a power law, C-m similar to T-eta, below 1.2 K with eta approximate to 2/3, which is consistent with a theoretical proposal of the presence of a spinon Fermi surface. Below 1.2 K, the mu SR relaxation rate shows no temperature dependence, suggesting persistent spin dynamics, as expected for a QSL state. Delving deeper, we also analyze longitudinal field mu SR spectra, revealing strong dynamical correlations in the spin-disordered ground state. All of these highlight the characteristics of spin entanglement in the QSL state.

Co_2C nanoparticles (NPs) are amongst transition metal carbides whose magnetic properties have not been well explored. A recent study by Nirmal Roy et al. [1] showed that a collection of Co_2C NPs exhibit an exchange bias (EB) effect below T_EB = 50 K and also a spin glass (SG) state below T_SG = 5 K. We use magnetic, electrical transport, specific heat, and muon spin rotation (μSR) measurements to explore further the magnetic properties of these NPs. We uncover the onset of Kondo localization at Kondo temperature T_K (= 40.1 K), near the onset of EB effect. A crossover from the Kondo-screened scenario to an RKKY interaction-dominated regime is also observed for T < T_K. Specific heat measurements confirm Kondo localization and heavy fermionic nature in Co_2C at low T. At low T, zero field μSR spectra reveal a dominant magnetically disordered fraction with slow relaxation and a smaller fraction with short-range order exhibiting fast relaxation, with no evidence of long-range magnetic order. We observe an increase in this fast relaxation rate between T_EB and T_SG, suggesting a slowing down of the fluctuating local magnetic environment around muons. Transverse field μSR spectra show the emergence of a stable, multi-peaked local magnetic field distribution below T_EB. Longitudinal field μSR spectra shows distinct changes in the dynamics of fluctuations suggesting the presence of a frozen glassy like state below 6 K. Our results suggest that below T_EB, Co_2C NPs pellet develops a magnetic interface, separating disordered and short-range order fractions. The Exchange interaction that sets in below T_EB at the interface couples them and suppresses the fluctuations. With the suppression of magnetic fluctuations below T_EB, strong correlation effects in the electronic state of Co_2C lead to Kondo localization.

We show the presence of magnetic rare regions consistent with the quantum Griffiths phase in Fe-doped MnSi using detailed heat capacity, magnetization, and muon spin relaxation (mu SR) measurements down to millikelvin temperatures. The slow dynamics of these rare regions at low temperatures leads to the non-Fermi-liquid behavior in heat capacity and magnetization. The mu SR and magnetization results further indicate that the dynamics freezes into a cluster-glass state below Tf similar to 1.25 K. The results are in agreement with theoretical models proposed in the literature for metallic systems with Heisenberg symmetry that exhibit the quantum Griffiths phase in the presence of strong disorder.

We probe the magnetic field-induced Tomonaga-Luttinger liquid (TLL) state in the bond-alternating spin-$1/2$ antiferromagnetic (AFM) chain compound NaVOPO$_4$ using thermodynamic as well as local $\mu$SR and $^{31}$P NMR probes down to milli-K temperatures in magnetic fields up to 14~T. The $\mu$SR and NMR relaxation rates in the gapless TLL regime decay slowly following characteristic power-law behaviour, enabling us to directly determine the interaction parameter $K$ as a function of the magnetic field. These estimates are cross-checked using magnetization and specific heat data. The field-dependent $K$ lies in the range of $0.4 < K < 1$ and indicates repulsive nature of interactions between the spinless fermions, in line with the theoretical predictions. This renders NaVOPO$_4$ the first experimental realization of TLL with repulsive fermionic interactions in hitherto studied $S=1/2$ bond-alternating AFM-AFM chain compounds.

Co 2 C nanoparticles (NPs) are amongst transition metal carbides whose magnetic properties have not been well explored. An earlier study (Roy et al 2021 J. Phys.: Condens. Matter 33 375804) showed that a pellet made from Co 2 C NPs exhibits exchange bias (EB) effect below a temperature, T EB = 50 K and a spin glass (SG) feature emerges below T SG = 5 K. In the current study we use magnetic, electrical transport, specific heat, and muon spin rotation ( μ SR) measurements to explore further the magnetic properties of a pellet made with 40 nm diameter pure Co 2 C NPs. We uncover the onset of Kondo localization at Kondo temperature T K (= 40.1 K), which is close to the onset temperature ( T EB ) of the EB effect. A crossover from the Kondo-screened scenario to the Ruderman–Kittel–Kasuya–Yosida interaction-dominated regime is also observed for T < T K . Temperature-dependent specific heat measurement further supports the Kondo localization scenario in the pellet and shows the heavy fermionic nature of the strongly correlated electronic state in Co 2 C. The zero field μ SR asymmetry spectra in the low-temperature regime are characterized by two distinct fast and slow relaxation rates. The spectra show the absence of long-range magnetic order in the sample. However, our analysis suggests the NPs-pellet shows the presence of a dominant magnetically disordered fraction and a smaller fraction with short-range order. Muons in the disordered fraction exhibit a slower relaxation rate, while muons in the smaller fraction with short-range order exhibit a faster relaxation rate. We observe an increase in this fast relaxation rate between T EB and T SG . This increase below T EB ∼ 50 K suggests a slowing down of the fluctuating local magnetic environment around muons. Transverse field- μ SR asymmetry spectra show the emergence of a stable, multi-peaked local magnetic field distribution in the pellet below T EB . Longitudinal field μ SR spectra shows distinct changes in the dynamics of fluctuations suggesting the presence of a frozen glassy like state below 6 K. Based on our results, we suggest that below T EB, the pellet of Co 2 C NPs develops a magnetic interface that separates the two magnetic fractions; one is a disordered fraction, and the other is a fraction with short-range order. The exchange interaction that sets in below T EB at the interface couples the two fractions, leading to a suppression of the fluctuations. With the suppression of magnetic fluctuations below T EB , strong correlation effects in the electronic state of Co 2 C lead to Kondo localization.

We present experimental and theoretical evidence of novel bound state formation in the low transverse field ordered phase of the quasi-one-dimensional Ising-like material CoNb_2O_6. High resolution single crystal inelastic neutron scattering measurements observe that small transverse fields lead to a breakup of the spectrum into three parts, each evolving very differently upon increasing field. This can be naturally understood starting from the excitations of the ordered phase of the transverse field Ising model, domain wall quasiparticles (solitons). Here, the transverse field and a staggered off-diagonal exchange create one-soliton hopping terms with opposite signs. We show that this leads to a rich spectrum and a special field, when the strengths of the off-diagonal exchange and transverse field match, at which solitons become localized; the highest field investigated is very close to this special regime. We solve this case analytically and find three two-soliton continua, along with three novel bound states. Perturbing away from this novel localized limit, we find very good qualitative agreement with the experimental data. We also present calculations using exact diagonalization of a recently refined Hamiltonian model for CoNb_2O_6 and using diagonalization of the two-soliton subspace, both of which provide a quantitative agreement with the observed spectrum. The theoretical models qualitatively and quantitatively capture a variety of non-trivial features in the observed spectrum, providing insight into the underlying physics of bound state formation.

Quasi-elastic neutron scattering (QENS) from bulk-water at 300 K, measured on the IRIS backscattering neutron spectrometer (ISIS, UK), is interpreted using the jump diffusion model (JDM), a “minimalistic” multi-timescale relaxation model (MRM) and molecular dynamics simulations (MD). In the case of MRM data analysis is performed in the time domain, where the relaxation of the intermediate scattering function is described by a stretched Mittag-Leffler function, E α (−(| t |/ τ ) α ). This function displays an asymptotic power law decay and contains the exponential relaxation function as a special case ( α = 1). To further compare the two approaches, MD simulations of bulk water were performed using the SPCE force field and the resulting MD trajectories analysed using the nMoldyn software. We show that both JDM and MRM accurately describe the diffusion of bulk water observed by QENS at all length scales, and confirm that MD simulations do not fully describe the quantum effects of jump diffusion.

Magnetism induced by defects in nominally non-magnetic solids has attracted intense scientific interest in recent years. The local magnetism in highly disordered undoped and Co-doped topological insulator (TI) Bi2Se3nanoplates has been investigated by muon spin relaxation (μSR). UsingμSR spectroscopy, together with other macroscopic characterizations, we find that these nanoplates are composed of a core with both static fields and dynamically fluctuating moments, and a shell with purely dynamically fluctuating moments. The fluctuations in the core die out at low temperatures, while those in the shell continue till 2 K. When Bi2Se3is doped with Co, the static magnetic component increases, whilst keeping the dual (static-plus-dynamic) nature intact. The findings indicate that highly disordered TI's could constitute a new class of promising magnetic materials that can be engineered by magnetic impurity doping.

With rising interest in organic-based functional materials, it is important to understand the nature of magnetic and electrical transitions within these types of systems. One intriguing material is triethylammonium bis-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)2) where there is an order-disorder transition at ∼220 K. This work focuses on novel neutron scattering techniques to understand the motion of the TEA cations at this transition and explain why we see the dielectric behaviour and possible ferroelectricity within this type of system. We show that the motion of the methyl groups of the TEA cation is spatially restricted below 220 K, whereas above the dielectric anomaly at 220 K, they are free to re-orientate, which ultimately leads to some rich behaviour that could be further exploited. Lastly, we also study the dynamics at this transition using a variety of additional techniques, helping to provide a consistent picture of the motions of the cations.

Bulk phase transformations and dislocation density were monitored in a maraging stainless steel on a bulk level using in-situ neutron diffraction up to 1340 degrees C, i.e. 30 degrees C below the melting temperature. Three materials with different initial microstructure and/or different composition were studied: wrought, as-built SLM-ed (selective laser melted) and re-austenitized SLM-ed. In contrast to the wrought martensitic steel, the as-built SLM-ed steel was essentially ferritic. However, re-austenitized SLM-ed steel recovered the usual martensitic microstructure. A delta-ferritic domain above 1200 degrees C was confirmed for all the materials studied. However, the amount of delta-ferrite at the melting point strongly depends upon steel composition. Additionally, it was shown that the initial microstructure of the steel (ferritic or martensitic) has little to no influence on re-austenization. Dislocation densities were estimated from diffraction peak broadening. The ferritic as-built SLM material contains a high dislocation density (similar to 4 x 10(14) m(-2)), which is however far less than in the martensitic materials (similar to 5 x 10(15) m(-2)). Dislocations start to annihilate from 550 degrees C / 600 degrees C in all the materials studied, but a measurable dislocation density of similar to 10(13) m(-2) is still observed at 950 degrees C / 1000 degrees C.