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Glycopyrronium bromide solid contact ion selective potentiometric sensors using multi-walled carbon nanotubes (MWCNTs), polyaniline nanoparticles (PANI NPs) and microparticles (PANI MPs) as ion-to-electron transducers were fabricated and compared to transducer free blank sensor. Their inclusion in solid contact (SC) sensors offer shorter response time, lower potential drift and longer life time. From a comparative point of view, inclusion of MWCNTs offer longer lifetime (50 days) to the SC sensor compared to PANI based SC sensors. While, the inclusion of PANI showed shorter response times. Hence, PANI-based sensors showed better stability on short term, while MWCNTs offered long term stability. PANI NPs gave faster response than MPs. This may be attributed to the higher surface/volume ratio in NPs which enlarges the contact area with the polymeric membrane, increasing the transduction at the interface. Moreover, PANI NPs showed lower potential drift and relatively longer life time than MPs. Nano-sized particles result in smooth surfaces with a good surface coverage (protection) of the underlying SC. The proposed sensors were successfully applied to content uniformity testing of GLY in a newly approved pharmaceutical dosage form with high accuracy.

CoO has an odd number of electrons in its unit cell, and therefore is expected to be metallic. Yet, CoO is strongly insulating owing to significant electronic correlations, thus classifying it as a Mott insulator. We investigate the magnetic fluctuations in CoO using neutron spectroscopy. The strong and spatially far-reaching exchange constants reported in [Sarte et al. Phys. Rev. B 98 024415 (2018)], combined with the single-ion spin-orbit coupling of similar magnitude [Cowley et al. Phys. Rev. B 88, 205117 (2013)] results in significant mixing between $j_{eff}$ spin-orbit levels in the low temperature magnetically ordered phase. The high degree of entanglement, combined with the structural domains originating from the Jahn-Teller structural distortion at $\sim$ 300 K, make the magnetic excitation spectrum highly structured in both energy and momentum. We extend previous theoretical work on PrTl$_{3}$ [Buyers et al. Phys. Rev. B 11, 266 (1975)] to construct a mean-field and multi-level spin exciton model employing the aforementioned spin exchange and spin-orbit coupling parameters for coupled Co$^{2+}$ ions on a rocksalt lattice. This parameterization, based on a tetragonally distorted type-II antiferromagnetic unit cell, captures both the sharp low energy excitations at the magnetic zone center, and the energy broadened peaks at the zone boundary. However, the model fails to describe the momentum dependence of the excitations at high energy transfers, where the neutron response decays faster with momentum than the Co$^{2+}$ form factor. We discuss such a failure in terms of a possible breakdown of localized spin-orbit excitons at high energy transfers., (main text - 21 pages, 12 figures; supplementary information - 15 pages, 3 figures, to be published in Phys. Rev. B)

The interplay of slight changes of the rare-earth composition and antiferromagnetic ordering of Cr in a series of high purity solid solutions of orthochromites with composition ${\mathrm{Ce}}_{1\ensuremath{-}x}\mathrm{Eu}{}_{x}{\mathrm{CrO}}_{3}\phantom{\rule{4pt}{0ex}}(1\ensuremath{\leqq}x\ensuremath{\leqq}0)$ was investigated by neutron and x-ray powder diffraction, magnetization, and heat capacity measurements. A careful study of the crystal structure by x-ray powder diffraction data across the whole range of $x$ enables us to correlate the magnetic properties of the Cr magnetic subsystem with the size of the lattice and minute changes of the bond and torsion angles within and between the ${\mathrm{CrO}}_{6}$ octahedra. We find that the sizes and the shapes of the ${\mathrm{CrO}}_{6}$ octahedra remain essentially unchanged as the size of the rare-earth cations and the cell volumes are gradually reduced by Eu substitution, whereas decreasing Cr-O-Cr bond angles and increasing inclination of neighboring octahedra compensate for the decreasing lattice size. Adverse to external hydrostatic pressure that reduces the cell volume but raises the ordering temperature, lowering the cell volume by replacing Ce by Eu decreases the N\'eel temperature linearly with the Eu concentration from 260 K for ${\mathrm{CeCrO}}_{3}$ to 178 K for ${\mathrm{EuCrO}}_{3}$.

We present the results of structural and magnetic phase comparisons of the iron oxychalcogenides ${\mathrm{La}}_{2}{\mathrm{O}}_{2}{\mathrm{Fe}}_{2}\mathrm{O}M{}_{2}(M=\text{S},\text{Se})$. Elastic neutron scattering reveals that $M=\text{S}$ and Se have similar nuclear structures at room and low temperatures. Our neutron diffraction data reveals that both materials obtain antiferromagnetic ordering at a N\'eel temperature ${T}_{N}90.1\phantom{\rule{4pt}{0ex}}\ifmmode\pm\else\textpm\fi{}0.16$ K and $107.2\ifmmode\pm\else\textpm\fi{}0.06$ K for $M=\text{Se}$ and S, respectively. The magnetic arrangements for both $M=\text{S}$, Se compounds are obtained through Rietveld refinement. We find the order parameter exponent $\ensuremath{\beta}$ to be 0.$129\ifmmode\pm\else\textpm\fi{}0.006$ for $M=\text{Se}$ and $0.133\ifmmode\pm\else\textpm\fi{}0.007$ for $M=\text{S}$. Each of these values is near the Ising symmetry value of 1/8. This suggests that although lattice and electronic structural modifications result from chalcogen replacement, the nature of the magnetic interactions is similar in these materials.

We have carried out inelastic neutron scattering experiments to study magnetic excitations in the ordered double perovskite ${\mathrm{Ca}}_{2}{\mathrm{FeReO}}_{6}$. We have found a well-defined magnon mode with a bandwidth of $\ensuremath{\sim}50$ meV below the ferrimagnetic ordering temperature (${T}_{c}\ensuremath{\sim}520$ K), similar to the previously studied ${\mathrm{Ba}}_{2}{\mathrm{FeReO}}_{6}$. The spin excitation is gapless for most temperatures within the magnetically ordered phase. However, a spin gap of $\ensuremath{\sim}10$ meV opens up below $\ensuremath{\sim}150$ K, which is well below the magnetic ordering temperature but coincides with a previously reported metal-insulator transition and onset of structural distortion. The observed temperature dependence of the spin gap provides strong evidence for ordering of Re orbitals at $\ensuremath{\sim}150$ K, in accordance with an earlier proposal put forward by K. Oikawa et al. based on neutron diffraction [J. Phys. Soc. Jpn. 72, 1411 (2003)] as well as recent theoretical work by Lee and Marianetti [Phys. Rev. B 97, 045102 (2018)]. The presence of separate orbital and magnetic ordering in ${\mathrm{Ca}}_{2}{\mathrm{FeReO}}_{6}$ suggests weak coupling between spin and orbital degrees of freedom and hints at a subdominant role played by spin-orbit coupling in describing its magnetism. In addition, we observed only one well-defined magnon band near the magnetic zone boundary, which is incompatible with simple ferrimagnetic spin waves arising from Fe and Re local moments but suggests a strong damping of the Re magnon mode.

Neutron spectroscopy was applied to study the magnetic interactions of orbitally degenerate Co2+ on a host MgO rocksalt lattice where no long-range spin or orbital order exists. The paramagnetic nature of the substituted monoxide Co0.03Mg0.97O allows for the disentanglement of spin exchange and spin-orbit interactions. By considering the prevalent excitations from Co2+ spin pairs, we extract seven exchange constants out to the fourth coordination shell. An antiferromagnetic next-nearest-neighbor 180◦ exchange interaction is dominant; however, dual ferromagnetic and antiferromagnetic interactions are observed for pairings with other pathways. These interactions can be understood in terms of a combination of orbital degeneracy in the t2g channel and the Goodenough-Kanamori-Anderson rules. Our work suggest that such a hierarchy of exchange interactions exists in transition-metal-based oxides with a t2g orbital degeneracy.

Inelastic neutron scattering has been used to study the magneto-elastic excitations in the multiferroic manganite hexagonal YMnO$_3$. An avoided crossing is found between magnon and phonon modes close to the Brillouin zone boundary in the $(a,b)$-plane. Neutron polarization analysis reveals that this mode has mixed magnon-phonon character. An external magnetic field along the $c$-axis is observed to cause a linear field-induced splitting of one of the spin wave branches. A theoretical description is performed, using a Heisenberg model of localized spins, acoustic phonon modes and a magneto-elastic coupling via the single-ion magnetostriction. The model quantitatively reproduces the dispersion and intensities of all modes in the full Brillouin zone, describes the observed magnon-phonon hybridized modes, and quantifies the magneto-elastic coupling. The combined information, including the field-induced magnon splitting, allows us to exclude several of the earlier proposed models and point to the correct magnetic ground state symmetry, and provides an effective dynamic model relevant for the multiferroic hexagonal manganites., Comment: 12 pages, 10 figures

The electronic phase diagram of the weak spin-orbit Mott insulator (Sr(1-x)Lax)3Ir2O7 is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antiferromagnetic, insulating regions and paramagnetic, metallic puddles persisting until x~0.04. Continued electron doping results in an abrupt, first-order phase boundary where the Neel state is suppressed and a homogenous, correlated, metallic state appears with an enhanced spin susceptibility and local moments. As the metallic state is stabilized, a weak structural distortion develops and suggests a competing instability with the parent spin-orbit Mott state., 5 pages, 4 figures

Neutron diffraction measurements are presented measuring the responses of both magnetic and structural order parameters of parent and lightly Co-doped Ba(${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}$)${}_{2}{\mathrm{As}}_{2}$ under the application of uniaxial pressure. We find that the uniaxial pressure induces a thermal shift in the onset of antiferromagnetic order that grows as a percentage of ${T}_{N}$ as Co doping is increased and the superconducting phase is approached. Additionally, as uniaxial pressure is increased within parent and lightly doped Ba(${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}$)${}_{2}{\mathrm{As}}_{2}$ on the first-order side of the tricritical point, we observe a decoupling between the onsets of the orthorhombic structural distortion and antiferromagnetism. Our findings place needed constraints on models exploring the nematic susceptibility of the bilayer pnictides in the tetragonal, paramagnetic regime.

Neutron diffraction is used to examine the polarization of weak static antiferromagnetism in high quality single crystalline URu2Si2. As previously documented, elastic Bragg-like diffraction develops for temperature T

We present neutron-scattering measurements on single crystals of lightly doped La${}_{2\ensuremath{-}x}$Ba${}_{x}$CuO${}_{4}$, with $0\ensuremath{\le}x\ensuremath{\le}0.035$. These reveal the evolution of the magnetism in this prototypical doped Mott insulator from a three-dimensional (3D) commensurate (C) antiferromagnetic ground state, which orders at a relatively high ${T}_{N}$, to a two-dimensional (2D) incommensurate (IC) ground state with finite-ranged static correlations, which appear below a relatively low effective ${T}_{N}$. At low temperatures, the 2D IC magnetism coexists with the 3D C magnetism for doping concentrations as low as $\ensuremath{\sim}$0.0125. We find no signal of a 3D C magnetic ground state by $x\ensuremath{\sim}0.025$, consistent with the upper limit of $x\ensuremath{\sim}0.02$ observed in the sister family of doped Mott insulators, La${}_{2\ensuremath{-}x}$Sr${}_{x}$CuO${}_{4}$. The 2D IC ground states observed for $0.0125\ensuremath{\le}x\ensuremath{\le}0.035$ are diagonal, and are rotated by 45 degrees within the orthorhombic basal plane compared with those previously reported for samples with superconducting ground states: La${}_{2\ensuremath{-}x}$Ba${}_{x}$CuO${}_{4}$, with $0.05\ensuremath{\le}x\ensuremath{\le}0.095$. We construct a phase diagram based solely on magnetic order-parameter measurements, which displays much of the complexity of standard high-temperature superconductivity phase diagrams discussed in the literature. Analysis of high-energy resolution inelastic neutron scattering at moderately low temperatures shows a progressive depletion of the very low-energy dynamic magnetic susceptibility as $x$ increases from 0.0125 to 0.035. This low-energy, dynamic susceptibility falls off with increasing temperature on a scale much higher than the effective 2D IC ${T}_{N}$ appropriate to these materials. Appreciable dynamic 2D IC magnetic fluctuations inhabit much of the ``pseudogap'' regime of the phase diagram.

We study the structural and magnetic orders in electron-doped BaFe2-xNixAs2 by high-resolution synchrotron x-ray and neutron scatterings. Upon Ni doping x, the nearly simultaneous tetragonal-to-orthorhombic structural (T-s) and antiferromagnetic (T-N) phase transitions in BaFe2As2 are gradually suppressed and separated, resulting in T-s > T-N with increasing x, as was previously observed. However, the temperature separation between T-s and T-N decreases with increasing x for x >= 0.065, tending toward a quantum bicritical point near optimal superconductivity at x approximate to 0.1. The zero-temperature transition is preempted by the formation of a secondary incommensurate magnetic phase in the region 0: 088 less than or similar to x less than or similar to 0.104, resulting in a finite value of T-N approximate to T-c + 10 K above the superconducting dome around x approximate to 0.1. Our results imply an avoided quantum critical point, which is expected to strongly influence the properties of both the normal and superconducting states.

Neutron diffraction measurements exploring the magnetic and structural phase behaviors of the candidate ${J}_{\mathrm{eff}}=1/2$ Mott insulating iridate Sr${}_{2}$IrO${}_{4}$ are presented. Comparisons are drawn between the correlated magnetism in this single-layer system and its bilayer analog Sr${}_{3}$Ir${}_{2}$O${}_{7}$, where both materials exhibit magnetic domains originating from crystallographic twinning and comparable moment sizes. Weakly temperature-dependent superlattice peaks violating the reported tetragonal space group of Sr${}_{2}$IrO${}_{4}$ are observed, supporting the notion of a lower structural symmetry arising from a high-temperature lattice distortion, and we use this to argue that moments orient along a unique in-plane axis demonstrating an orthorhombic symmetry in the resulting spin structure. Our results demonstrate that the correlated spin order and structural phase behaviors in both single-layer and bilayer Sr${}_{n+1}$Ir${}_{n}$O${}_{3n+1}$ systems are remarkably similar and suggest comparable correlation strengths in each system.

We report inelastic neutron scattering measurements in the hidden order state of URu${}_{2\ensuremath{-}x}$Re${}_{x}$Si${}_{2}$ with $x=0.10$. We observe that towards the ferromagnetic quantum critical point induced by the negative chemical pressure of Re doping, the gapped incommensurate fluctuations are robust and comparable in intensity to the parent material. As the Re doping moves the system toward the quantum critical point, the commensurate spin fluctuations related to hidden order weaken, display a shortened lifetime, and slow down. Halfway to the quantum critical point, the hidden order phase survives, albeit weakened, in contrast to its destruction by hydrostatic pressure and by positive chemical pressure from Rh doping.

Through a neutron scattering, charge transport, and magnetization study, the correlated ground state in the bilayer iridium oxide Sr${}_{3}$Ir${}_{2}$O${}_{7}$ is explored. Our combined results resolve scattering consistent with a high temperature magnetic phase that persists above 600 K, reorients at the previously defined ${T}_{\text{AF}}=280$ K, and coexists with an electronic ground state whose phase behavior suggests the formation of a fluctuating charge or orbital phase that freezes below ${T}^{*}\ensuremath{\approx}70$ K. Our study provides a window into the emergence of multiple electronic order parameters near the boundary of the metal to insulator phase transition of the $5d$ ${J}_{\text{eff}}=1/2$ Mott phase.

We report neutron scattering experiments probing the influence of uniaxial strain on both the magnetic and structural order parameters in the parent iron pnictide compound, BaFe$_2$As$_2$. Our data show that modest strain fields along the in-plane orthorhombic b-axis can affect significant changes in phase behavior simultaneous to the removal of structural twinning effects. As a result, we demonstrate in BaFe$_2$As$_2$ samples detwinned via uniaxial strain that the in-plane C$_4$ symmetry is broken by \textit{both} the structural lattice distortion \textit{and} long-range spin ordering at temperatures far above the nominal (strain-free), phase transition temperatures. Surprising changes in the magnetic order parameter of this system under relatively small strain fields also suggest the inherent presence of magnetic domains fluctuating above the strain-free ordering temperature in this material., 4 pages, 3 figures

Nuclear magnetic resonance (NMR) measurements of $\mathrm{CuO}$ chains of detwinned ortho-II ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.5}$ (YBCO6.5) single crystals reveal unusual and remarkable properties. The chain Cu resonance broadens significantly, but gradually, on cooling from room temperature. The line shape and its temperature dependence are substantially different from that of a conventional spin/charge density wave (S/CDW) phase transition. Instead, the line broadening is attributed to small amplitude static spin and charge density oscillations with spatially varying amplitudes connected with the ends of the finite length chains. The influence of this $\mathrm{CuO}$ chain phenomenon is also clearly manifested in the plane Cu NMR.

We have mapped the neutron scattering spin spectrum at low energies in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.353}$ $({T}_{c}=18\phantom{\rule{0.3em}{0ex}}\mathrm{K})$, where the doping $\ensuremath{\sim}0.06$ is near the critical value $({p}_{c}=0.055)$ for superconductivity. No coexistence with long-range-ordered antiferromagnetism is found. The spins fluctuate on two energy scales: one a damped spin response with a $\ensuremath{\simeq}2\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ relaxation rate and the other a central mode with a relaxation rate that slows to less than $0.08\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ below ${T}_{c}$. The spectrum mirrors that of a soft mode driving a central mode. Extremely short correlation lengths, $42\ifmmode\pm\else\textpm\fi{}5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ in-plane and $8\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ along the $c$ direction, and isotropic spin orientations for the central mode indicate that the correlations are subcritical with respect to any second-order transition to N\'eel order. The dynamics follows a model where damped spin fluctuations are coupled to the slow fluctuations of regions with correlations shortened by the hole doping.