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The inelastic neutron scattering spectra recorded in this study and elsewhere provide a useful set of crystal-field (CF) energy levels for the ground J = 6 term of Ho3+ in HoFeO3. The resolution of the low-energy, temperature-dependent pseudo-quadrupole ground state splitting and magnon peaks is consistent with the self-ordering of the Ho3+ sublattice at T Ho ∼ 8–10 K and supports earlier electron spin resonance investigations of the Ho3+ magnon behaviour. Systematic analysis of the grouped singlet CF levels of Ho3: HoFeO3, in conjunction with the CF Kramers doublet levels of the neighbouring Er3+: ErFeO3, has yielded possible sets of CF parameters for the two systems.

The present work described the first voltammetric sensor for the estimation of indacaterol (IND) in the presence of its co-formulated drug glycopyrronium bromide. Indacaterol (IND) is used to treat chronic obstructive pulmonary disease, which is a major cause of morbidity and mortality worldwide so the quick analysis of minor concentrations of this drug is very important. Titanium(IV) oxide nanoparticles (TiO2-NPs) and the ionic liquid (IL) n-hexyl-3-methylimidazolium hexafluorophosphate were used for the new formulated carbon paste electrode. Other factors, such as the pH of the solution, the TiO2-NP concentration and the scan rate, were also optimized using cyclic voltammetry. Scanning electron microscopy, chronoamperometry and electrochemical impedance spectroscopy were utilized for determination of the character of the electrochemical sensor. Moreover, the electrochemical redox mechanism of IND at the proposed sensor was studied. Under the optimum conditions, the proposed TiO2-NP–IL–MCPE showed good linearity over a concentration range of 2.00 nM–200.00 mM using square wave voltammetry. The LOD was found to be 500 pM, indicating excellent sensitivity. Satisfactory recoveries of IND from pharmaceutical formulations, content uniformity tests and human plasma and urine were achieved, clearly revealing that the new sensor can be used in the clinical analysis of IND and in quality control laboratories.

An efficient and fast microwave-assisted extraction (MAE) technique was developed for extracting gallic acid as an indicative biomarker for the quality control of Acacia arabica bark. The MAE technique was optimized and compared with other conventional extraction techniques. The optimal conditions of MAE were 20% methanol as solvent, solid/liquid ratio 1:40 (g/mL), irradiation power 20% and two extraction cycles, 5 min each. The proposed extraction technique produced a maximum yield of 10.59 (mg/g) gallic acid in 10 min, which was 1.03 and 1.15 times more efficient than 6 h of heat reflux and 24 h of maceration extraction, respectively. This high yield, along with saving of time, energy, and solvent would position MAE as a valuable and cost-effective technology suitable for today's highly competitive industries, with growing demand for increased productivity, improved efficiency, and reduced cycle time. Moreover, a new high-performance liquid chromatography method was developed and validated for the determination of gallic acid in Acacia arabica bark extract. The method was found to be rapid, sensitive, accurate, precise, and robust. The method showed good linearity over concentration range 1-100 (µg/mL) with LOD 16.08 (ng/mL) and LOQ 48.73 (ng/mL). The average recovery obtained using standard addition technique was 100.36% with a low value of RSD% (1.19%) indicating the accuracy of the proposed method for determination of gallic acid in Acacia arabica bark extract.

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)

Non-invasive methods have been a big part of research due to their low cost and because they are more convenient for the patient and healthcare providers. Detecting Iron Deficiency-Anemia early plays a significant role in a person’s health, and it is done usually by blood withdraw and performing a CBC test. In this research, we explore different non-invasive and less-invasive techniques developed to measure hemoglobin concentration. We then evaluate them mathematically and clinically based on various evaluation measures. Finally, we give our proposed alternative technique which was designed to be less costly, more accurate across a wide range (6–14 g/dL), and portable.

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.

Three spectrophotometric methods have been developed and validated for determination of indacaterol (IND) and glycopyrronium (GLY) in their binary mixtures and novel pharmaceutical dosage form. The proposed methods are considered to be the first methods to determine the investigated drugs simultaneously. The developed methods are based on different signal processing techniques of ratio spectra namely; Numerical Differentiation (ND), Savitsky-Golay (SG) and Fourier Transform (FT). The developed methods showed linearity over concentration range 1-30 and 10-35 (μg/mL) for IND and GLY, respectively. The accuracy calculated as percentage recoveries were in the range of 99.00%-100.49% with low value of RSD% (

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.

An efficient and fast microwave-assisted extraction (MAE) technique was developed for extracting trigonelline as an indicative biomarker for the quality control of Trigonella foenum-graecum seeds. The MAE procedure was optimized and compared with other conventional extraction techniques. The optimal conditions of MAE were 50% methanol as solvent, solid—liquid ratio 1:20 g mL−1, irradiation power 40%, and two extraction cycles, 3 min each. The proposed extraction technique produced a maximum yield of 7.89 mg g−1 trigonelline in 6 min which was 1.28 and 2.20 times more efficient than 3 h of heat reflux and 15 h of maceration extraction, respectively. Furthermore, rapid high-performance thin-layer chromatographic and high-performance liquid chromatographic methods for the quantification of trigonelline were established and validated. The methods were found to be simple, sensitive, precise, accurate, and specific for the estimation of trigonelline in T. foenum-graecum seeds extract and overcame disadvantages of previously published methods.

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 automotive air conditioning compressor (AAC) is belt-driven by the engine. The compressor speed is directly proportional to the engine speed. Therefore, the cooling capacity will vary as the engine speed changes. To meet the air conditioning (AC) demand, the compressor continually cycles on and off. In the research, the compressor of the AAC is driven by an electric motor which in turn is operated by electrical battery (12 volt). The use of direct current compressor (DCC) is seen as a solution of the existing system. Using the proposed system, DCC gets significant improvements in energy efficiency. Compared with AAC system, the energy conservation effect is about 77.5% to 86.35%.

We carried out detailed studies of the magnetic structure, magnetoelastic coupling, and thermal properties of ${\mathrm{EuCrO}}_{3}$ nanopowders from room temperature to liquid helium temperature. Our neutron powder diffraction and x-ray powder diffraction measurements provide precise atomic positions of all atoms in the cell, especially for the light oxygen atoms. The low-temperature neutron powder diffraction data revealed extra Bragg peaks of magnetic origin, which can be attributed to a ${G}_{x}$ antiferromagnetic structure with an ordered moment of $\ensuremath{\sim}2.4{\ensuremath{\mu}}_{\mathrm{B}}$ consistent with the $3{d}^{3}$ electronic configuration of the ${\mathrm{Cr}}^{3+}$ cations. Apart from previously reported antiferromagnetic and ferromagnetic transitions in ${\mathrm{EuCrO}}_{3}$ at low temperatures, we also observed an anomaly at about 100 K. This anomaly was observed in the temperature dependence of the sample's, lattice parameters, thermal expansion, Raman spectroscopy, permittivity, and conductance measurements. This anomaly is attributed to the magnetoelastic distortion in the ${\mathrm{EuCrO}}_{3}$ crystal.

Magnetic and phonon excitations in the antiferromagnet CoO with an unquenched orbital angular momentum are studied by neutron scattering. Results of energy scans in several Brillouin zones in the (HHL) plane for energy transfers up to 16 THz are presented. The measurements were performed in the antiferromagnetic ordered state at 6 K (well below TN ∼290 K) as well as in the paramagnetic state at 450 K. Several magnetic excitation modes are identified from the dependence of their intensity on wavevector and temperature. Within a Hund’s rule model, the excitations correspond to fluctuations of coupled orbital and spin degrees of freedom, whose bandwidth is controlled by interionic superexchange. The different ordering domains give rise to several magnetic peaks at each wavevector transfer.

We perform a combined experimental-theoretical study of the Fe-oxychalcogenides (FeO$\emph{Ch}$) series La$_{2}$O$_{2}$Fe$_{2}$O\emph{M}$_{2}$ (\emph{M}=S, Se), which is the latest among the Fe-based materials with the potential \ to show unconventional high-T$_{c}$ superconductivity (HTSC). A combination of incoherent Hubbard features in X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS) spectra, as well as resitivity data, reveal that the parent FeO$\emph{Ch}$ are correlation-driven insulators. To uncover microscopics underlying these findings, we perform local density approximation-plus-dynamical mean field theory (LDA+DMFT) calculations that unravel a Mott-Kondo insulating state. Based upon good agreement between theory and a range of data, we propose that FeO$\emph{Ch}$ may constitute a new, ideal testing ground to explore HTSC arising from a strange metal proximate to a novel selective-Mott quantum criticality.

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

In this study, we use nuclear magnetic resonance (NMR), high-resolution x-ray and neutron scattering to study structural and magnetic phase transitions in phosphorus-doped BaFe2(As1-xPx)2. Thus, previous transport, NMR, specific heat, and magnetic penetration depth measurements have provided compelling evidence for the presence of a quantum critical point (QCP) near optimal superconductivity at x = 0.3. However, we show that the tetragonal-to-orthorhombic structural (Ts) and paramagnetic to antiferromagnetic (AF, TN) transitions in BaFe2(As1-xPx)2 are always coupled and approach to TN ≈ Ts ≥ Tc (≈ 29 K) for x = 0.29 before vanishing abruptly for x ≥ 0.3. These results suggest that AF order in BaFe2(As1-xPx)2 disappears in a weakly first order fashion near optimal superconductivity, much like the electron-doped iron pnictides with an avoided QCP.

We use nuclear magnetic resonance (NMR), high-resolution x-ray, and neutron scattering studies to study structural and magnetic phase transitions in phosphorus-doped BaFe2(As(1-x)P(x)2. Previous transport, NMR, specific heat, and magnetic penetration depth measurements have provided compelling evidence for the presence of a quantum critical point (QCP) near optimal superconductivity at x=0.3. However, we show that the tetragonal-to-orthorhombic structural (T{s}) and paramagnetic to antiferromagnetic (AF, TN) transitions in BaFe2(As(1-x)Px)2 are always coupled and approach T{N}≈T{s}≥T{c} (≈29 K) for x=0.29 before vanishing abruptly for x≥0.3. These results suggest that AF order in BaFe_{2}(As(1-x)Px)2 disappears in a weakly first-order fashion near optimal superconductivity, much like the electron-doped iron pnictides with an avoided QCP.

Author(s): Dhital, C; Hogan, T; Yamani, Z; Birgeneau, RJ; Tian, W; Matsuda, M; Sefat, AS; Wang, Z; Wilson, SD

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

Ceramic Gd1−x Pr x Ba2Cu3O7−y (GdPr-123) high-T c superconductors have been synthesized by the standard solid state reaction method and characterized by XRD, SEM, TGA, and DT techniques in the range of x, 0.0 ≤ x ≤ 1.0 Samples have orthorhombic structure with Pmmm symmetry and there is a small percentage (less than 1%) of the Ba sites occupied by Pr ions in some Pr-rich samples. In these samples a small trace of BaCuO2 and Pr BaO3 secondary phases persist with the main peaks at 2θ = 29.3° and 28.9° respectively. Microstructure analysis indicates a uniform grain size distribution with a mean size of 5 μm. No significant change of grain size is shown throughout the range of x studied. The valence of Pr and Cu were determined by magnetization measurements in the temperature range 100 to 250°K. These data reveal a valence of 3.86+ for Pr in all samples independant of x. The similarity of the superconducting and insulating properties in this system to those of the oxygen deficient RBa2Cu3O7 (R-123) (R...

The ceramic compounds Gd1-xPrxCu3O7-y (GdPr-123) with 0.0 ≤x≤1.0, were synthesized by standard solid state reaction technique. XRD analysis shows a predominantly single phase perovskite structure with the orthorhombic Pmmm symmetry. The samples have been examined for superconductivity by measuring electrical resistivity within the temperature range 10–300 K. These measurements show a suppression of superconductivity with increasing x. It is observed that the critical Pr concentration (xcr) required to suppress superconductivity is about 0.45, the samples with x

An extensive study of magnetic, electrical transport, and structural properties of the normal and superconducting states of Gd${}_{1\ensuremath{-}x}$Pr${}_{x}$Ba${}_{2}$Cu${}_{3}$O${}_{7\ensuremath{-}y}$ (GdPr-123) are presented. Ceramic compounds have been synthesized by the solid-state reaction technique, and characterized by x-ray-diffraction, scanning-electron-microscopy, thermogravimetric, and differential-thermal analyses. The superconducting transition temperature is reduced with increasing Pr content $x$ in a nonlinear manner, in contrast to Abrikosov-Gor'kov pair-breaking theory. Magnetic susceptibility measurements show that the nominal Pr valence is 3.86+, independently of $x$. A metal-insulator transition is observed at ${x}_{\mathrm{cr}}\ensuremath{\approx}0.45$, similar to that in the oxygen-deficient $R{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}$ $(R$-123) system. Based on this resemblance, we suggest that both Pr doping and oxygen deficiency act through the same mechanism. Hence, the environment surrounding the CuO${}_{2}$ layers is important to high-${T}_{c}$ superconductivity (HTSC). In this sense, HTSC cannot completely be a two-dimentional feature. A chain-plane-correlation effect is plausible.

An extensive study of the magnetic, electrical transport, and structural properties of the normal and superconducting states of Gd 1-x Pr x Ba 2 Cu 3 O 7-y (GdPr-123) is presented. Ceramic compounds have been synthesized by the solid state reaction technique, and characterized by XRD, SEM, TGA, and DT techniques. The parent compound GdBa 2 Cu 3 O 7-y (Gd-123) is a high-T c superconductor and the endpoint compound, PrBa 2 Cu 3 O 7-y (Pr-123) is a magnetic insulator, both having the crystal structures isomorphic to the 123 phase structure. The superconducting transition temperature is reduced with increasing Pr content in a non-linear manner, in contrast to the Abrikosov-Gorkov pair breaking theory. A metal-insulator transition is observed at the critical Pr content, X ct 0.45, at which superconductivity completely disappears. Magnetic susceptibility measurements show that the nominal Pr valence is 3.86+, independent of the Pr content. The metal-insulator transition in this system is similar to that in the oxygen-deficient RBa 2 Cu 3 O 7-y (R-123) system. Based on this resemblance, we suggest that Pr doping reduces the carrier concentration (either by hole filling/localization or changes in the band structure) similar to the deoxygenated case. Hence, the environment surrounding the Cu-O layers is important to high-T c superconductivity (HTSC). In this sense, HTSC cannot completely be two dimensional feature. A chain-plane correlation (CPC) effect is plausible. The normal state conduction mechanism has been interpreted by the quantum percolation theory based on localized states. Localization is probably caused by the Pr valence fluctuations in the GdPr-123 system.

The Gd - Pr solid solution of the `123' crystal structure, (GdPr-123) with has been prepared by the standard solid-state reaction technique. Details of sample preparation and results of XRD, SEM, TGA, DT, , and measurements are reported. For , GdPr-123 is non-superconducting down to 10 K and does not show `metallic' conduction. Samples have a predominantly single-phase orthorhombic structure with Pmmm symmetry and a small percentage () of the Ba sites are occupied by Pr ions in some Pr-rich samples. The lower critical field value measured lies in the range of 10 mT. The nominal valence of the Cu ion in the whole range of x is determined; at the metal - semiconductor boundary , which is smaller by only 0.18 than the value 2.33 of the fully oxygenated (Gd-123) system. However, the valence of Pr is 3.86+. We suggest that the increasing band filling and localization of states due to the disorder effects together with Pr doping could cause the observed metal - semiconducting transition; qualitatively this is the same as the oxygen depletion case.

Neutron scattering is used to investigate the single-ion spin and orbital excitations below the Mott-Hubbard gap in CoO. Three excitations are reported at $0.870\ifmmode\pm\else\textpm\fi{}0.009$ eV, $1.84\ifmmode\pm\else\textpm\fi{}0.03$, and $2.30\ifmmode\pm\else\textpm\fi{}0.15$ eV. These were parametrized within a weak crystal field scheme with an intraorbital exchange of $J(dd)=1.3\ifmmode\pm\else\textpm\fi{}0.2$ eV and a crystal field splitting $10Dq=0.94\ifmmode\pm\else\textpm\fi{}0.10$ eV. A reduced spin-orbit coupling of $\ensuremath{\lambda}=\ensuremath{-}0.016\ifmmode\pm\else\textpm\fi{}0.003$ eV is derived from dilute samples of Mg${}_{0.97}$Co${}_{0.03}$O, measured to remove effects due to spin exchange and structural distortion parameters which break the cubic phase degeneracy of the orbital excitations complicating the inelastic spectrum. The peak at 1.84 eV, while reported using resonant x-ray and optical techniques, was absent or weak for nonresonant x-ray experiments and overlaps with the expected position of a ${}^{4}{A}_{2}$ level. This transition is absent in the dipolar approximation but expected to have a finite quadrupolar matrix element that can be observed with neutron scattering techniques at larger momentum transfers. Our results agree with a crystal field analysis (in terms of Racah parameters and Tanabe-Sugano diagrams) and with previous calculations performed using local-density band theory for Mott insulating transition metal oxides. The results also demonstrate the use of neutron scattering for measuring dipole forbidden transitions in transition metal oxide systems.

Interest in many strongly spin-orbit coupled 5d-transition metal oxide insulators stems from mapping their electronic structures to a J=1/2 Mott phase. One of the hopes is to establish their Mott parent states and explore these systems' potential of realizing novel electronic states upon carrier doping. However, once doped, little is understood regarding the role of their reduced Coulomb interaction U relative to their strongly correlated 3d-electron cousins. Here we show that, upon hole-doping a candidate J=1/2 Mott insulator, carriers remain localized within a nanoscale phase separated ground state. A percolative metal-insulator transition occurs with interplay between localized and itinerant regions, stabilizing an antiferromagnetic metallic phase beyond the critical region. Our results demonstrate a surprising parallel between doped 5d- and 3d-electron Mott systems and suggest either through the near degeneracy of nearby electronic phases or direct carrier localization that U is essential to the carrier response of this doped spin-orbit Mott insulator., 25 pages, 4 figures in main text, 4 figures in supplemental text

Interest in many strongly spin-orbit-coupled 5d-transition metal oxide insulators stems from mapping their electronic structures to a J(eff)=1/2 Mott phase. One of the hopes is to establish their Mott parent states and explore these systems' potential of realizing novel electronic states upon carrier doping. However, once doped, little is understood regarding the role of their reduced Coulomb interaction U relative to their strongly correlated 3d-electron cousins. Here we show that, upon hole-doping a candidate J(eff)=1/2 Mott insulator, carriers remain localized within a nanoscale phase-separated ground state. A percolative metal-insulator transition occurs with interplay between localized and itinerant regions, stabilizing an antiferromagnetic metallic phase beyond the critical region. Our results demonstrate a surprising parallel between doped 5d- and 3d-electron Mott systems and suggest either through the near-degeneracy of nearby electronic phases or direct carrier localization that U is essential to the carrier response of this doped spin-orbit Mott insulator.

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 study the structural and magnetic orders in electron-doped BaFe(2-x)Ni(x)As2 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≈0.1. The zero-temperature transition is preempted by the formation of a secondary incommensurate magnetic phase in the region 0.088≲x≲0.104, resulting in a finite value of T(N)≈T(c) + 10 K above the superconducting dome around x≈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.

The magnetic ordering of nanocrystalline gadolinium (crystallite sizes of 21 nm and 38 nm) has been studied using neutron diffraction and compared with that of a reference ($\ensuremath{\sim}1\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$) sample. In contrast with bulk gadolinium in which the moments order initially parallel to the $c$-axis and then cant by as much as ${60}^{\ensuremath{\circ}}$ away from the $c$-axis below 250 K, before rotating back towards the $c$-axis on further cooling, both nanocrystalline samples order with their moments canted by about ${50}^{\ensuremath{\circ}}$ from the $c$-axis, and this canting angle is largely temperature independent.

Predominantly single phase polycrystalline Gd 1− x Pr x Ba 2 Cu 3 O 7− y (GdPr-123) samples with 0 ≤ x ≤ 1.0 have been prepared by standard solid state reaction technique and characterized by XRD. The electrical resistivity measurements show the suppression of superconductivity with increasing x . Two plateaus appear in the T c versus x curve at x ≈ 0−0.05 and at x ≈ 0.15−0.25 followed by a decrease to zero at x cr ≈ 0.45, similar to the plateaus of T c versus 7 − y curve at 7 − y ≈ 6.8 −7 and at 7 − y ≈ 6.55−6.75 in R Ba 2 Cu 3 O 7 − y ( R -123) ( R : Y or rare earth except Ce, Pr, Pm, Tb) systems. The valency of Pr was determined by magnetization measurements in the temperature range 100 K to 250 K. This data indicates a mixed valence state for Pr ions with an effective magnetic moment μ ≈ 2.69 μ B per Pr ion, which yields a valency for Pr of ≈ 3.86 +. For these systems, T c ( x ) does not follow the Abrikosov-Gor'kov pair breaking theory. We suggest that the suppression of superconductivity by Pr-substitution can be explained by means of an effective increasing of the oxygen deficiency in the structure, in a similar way to what happens in an R -123 system, when 7 − y is decreased in a controlled manner. This implies that CuO 2 planes are responsible for superconductivity through the effect of chains.