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Quasi-one-dimensional topological materials have emerged as a captivating area of research due to their interesting electronic properties and potential applications. NbNiTe 5 is one such quasi-1D material. In this work, we report the synthesis, structural characterization, and comprehensive investigation of the electrical transport and magnetic properties of NbNiTe 5. NbNiTe 5 crystallizes in the orthorhombic crystal system with the C m c m space group. Experimental studies have uncovered metallic nature with a remarkably high residual resistivity ratio of 103, along with intriguing spin–orbit interaction-driven nonsaturating magnetotransport properties at low temperatures. A meticulous analysis incorporating magnetoconductivity measurements unveils signatures of weak anti-localization analyzed by using the Hikami–Larkin–Nagaoka formula. Furthermore, the de Haas–van Alphen oscillations demonstrate the high mobility of charge carriers with a significantly low effective mass at five frequencies: F α = 84.82 T, F β = 131.21 T, F γ = 242.36 T, F δ = 31.93 T, and F δ ′ = 162.33 T. In light of these collective findings, NbNiTe 5 can be defined as a quasi-1D topological semimetal. [ABSTRACT FROM AUTHOR]

In this study, we synthesized colloidal copper nanoparticles (CuNPs) utilizing Q-switched Nd:YAG laser ablation on a copper plate immersed in double-distilled water at energies of 200 and 400 mJ, respectively, with 100, 200, 300, 400, and 500 pulses. The size and optical properties of nanoparticles were determined using a UV–Vis spectrophotometer, a transmission electron microscope (TEM), and a field emission scanning electron microscope (FE-SEM). The absorption spectra exhibited two surface plasmon resonance peaks (λSPR), one at 217 nm for copper oxide nanoparticles (CuONPs) and the other at 636 nm for CuNPs, with the increase in laser pulses. Consequently, the optical bandgap increased by roughly 3 eV. The TEM and FE-SEM analyses showed nearly spherical Cu nanoparticles with average diameters of 33 and 38 nm for laser energies of 200 and 400 mJ, respectively. An analysis of x-ray diffraction patterns revealed that CuONPs contained the crystallographic planes of a monoclinic and an orthorhombic crystal system. Additionally, the mean crystallite size of laser-ablated nanoparticles increased with increasing pulse energy. Furthermore, the absorption and optical bandgap of CuNPs increased slightly with an increase in ultraviolet irradiation exposure. The results of our study showed an increased inhibitory effect against both Staphylococcus aureus bacteria and Escherichia coli bacteria when CuNPs were irradiated by ultraviolet type C. [ABSTRACT FROM AUTHOR]

A solid solution between relaxor ferroelectric PbMg1/3Nb2/3O3 (PMN) and multiferroic BiFeO3 (BFO) has been synthesized by a solid-state chemical reaction route. The comprehensive x-ray diffraction studies of (1 − x)PbMg1/3Nb2/3O3–xBiFeO3 [(1 − x)PMN–xBFO] confirm the realization of stable and orthorhombic crystal systems. From the dielectric study, relaxor behavior has been observed, which is corroborated by a broadened peak and diffusive phase transition. The magnetoelectric (ME) properties have been explored through P–E loop, M–H loop, and magnetoelectric coefficient analyses. The simultaneous occurrence of polarization and magnetization reveals the ME coupling response of the PMN–BFO compounds. Excellent values of PS = 15.94 μc/cm2, Pr = 7.68 μc/cm2, MS = 12.96 emu/g, Mr = 1.25 emu/g, and ME coefficient value of 220 mV/cm Oe for x = 0.3 are obtained, which is helpful for magnetoelectric field sensor applications. To ascertain its sensing capability, a prototype has been developed, and the sensing behavior of the device has been established by placing it near a designed helical coil electromagnetic field generator structure. [ABSTRACT FROM AUTHOR]

A superhard carbon phase with Pmmm (D2h1, 47) symmetry is predicted by using a recently developed particle swarm optimization method for searching for crystal structures. The carbon phase is an orthorhombic crystal system that contains 16 atoms per unit cell, named oC16, which has an all-sp3-hybridized bonding network and contains a large cavity. oC16 has a distinct topology, including zigzag four-, five-, six-, and eightfold carbon rings. The dynamic, elastic, and electronic properties of oC16 are investigated by first-principles calculations, and the results show that oC16 is more energetically stable than the experimentally synthesized T-carbon, BC8, and BC12. The phonon spectra and elastic constants confirm its dynamical and mechanical stability at zero pressure, respectively. The calculated bulk moduli and hardness indicate that oC16 is an ultra-incompressible and superhard material. Analyzing its electronic band structure reveals that oC16 has insulation characteristics with an indirect bandgap of 4.42 eV. Also investigated is how the elastic moduli of the oC16 phase depend on the crystal orientation. Because of its superhard and porous properties, the potential uses of oC16 include hydrogen storage, molecular sieves, coating, and tools for cutting, polishing, and grinding. [ABSTRACT FROM AUTHOR]

The applicability of an atomistic Class II force field to capture the properties of the orthorhombic crystal phase of ammonium perchlorate was investigated. Structural and dynamical behaviors including density, lattice parameters, bulk modulus, infrared spectrum, and rotational dynamics were calculated from the trajectories of molecular dynamics (MD) simulations. Properties calculated from MD were compared to available experimental data over a range of temperatures, including those significantly higher than the parameterization temperature of 10 K. [ABSTRACT FROM AUTHOR]

By means of ab initio computations and the global minimum structure search method, we have investigated structural, mechanical, and electronic properties of D-carbon, a crystalline orthorhombic sp³ carbon allotrope (space group Pmma [D2h5] with 6 atoms per cell). Total-energy calculations demonstrate that D-carbon is energetically more favorable than the previously proposed T6 structure (with 6 atoms per cell) as well as many others. This novel phase is dynamically, mechanically, and thermally stable at zero pressure and more stable than graphite beyond 63.7 GPa. D-carbon is a semiconductor with a bandgap of 4.33 eV, less than diamond's gap (5.47 eV). The simulated X-ray diffraction pattern is in satisfactory agreement with previous experimental data in chimney or detonation soot, suggesting its possible presence in the specimen. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]

Electron spin resonance (ESR) spectra of surface and interface recombination centers recently observed on (001) silicon wafers, labeled Pm and KU1, were studied using spin dependent microwave photoconductivity. Both ESR spectra, having the orthorhombic symmetry and spins S =1/2 and S =1 for Pm and KU1, respectively, were observed in the commercially available surface oxidized (001)-Si wafers. Systematic studies on annealing and oxidation conditions for the Pm and KU1 formation conclude that both ESR spectra arise from the same center that contains the interaction between the two nearest Si dangling bonds on the (001) Si surface. [ABSTRACT FROM AUTHOR]

Industrial processes involving the manufacture of heat treatment salts such as BaCl at high pressures are becoming possible. Hence, there is a need to search for a specific form of BaCl with excellent thermal properties. Motivated by this, the potential energy surface of BaCl is extensively explored using the unbiased particle swarm-intelligence optimization algorithm to uncover a global minimum enthalpy phase of BaCl within the pressure range that was recently experimentally explored. Previously predicted phases were confirmed during the structure search. Furthermore, the orthorhombic Pnma form of BaCl is predicted to be more stable and energetically more favorable than the previously predicted R-3m phase in the pressure range of ~10–15 GPa. The electronic and thermal properties of the newly discovered phase are extensively studied using first principles calculations. In the pressure range of interest, Pnma BaCl is metallic and nonmagnetic. More so, the solution of the Boltzmann Transport Equation unravels promising thermal properties, which make Pnma BaCl a good candidate for heat management in high temperature systems. We found the overall Grüneisen parameters in Pnma BaCl to range between 0.963 and 0.995 and the lattice thermal conductivity at 300K to be 53.7W m–1K–1. We also found that Pnma BaCl exhibits anisotropy that we observed is constant in all directions explored. [ABSTRACT FROM AUTHOR]

Gallium (Ga) doped silicon (Si) is becoming a relevant player in solar cell manufacturing thanks to its demonstrated low light-induced degradation, yet little is known about Ga-related recombination centers. In this paper, we study iron (Fe)-related recombination centers in as-grown, high quality, directionally solidified, monocrystalline Ga-doped Si. While no defect states could be detected by deep level transient spectroscopy, lifetime spectroscopy analysis shows that the minority carrier lifetime in as-grown wafers is dominated by low levels of FeGa related defect complexes. FeGa pairs have earlier been shown to occur in two different structural configurations. Herein, we show that in terms of recombination strength, the orthorhombic pair-configuration is dominant over the trigonal pairconfiguration for FeGa. Furthermore, the defect energy level in the band gap for the orthorhombic defect center is determined to be EVþ0.09 eV, and the capture cross-section ratio of the same defect center is determined to be 220. [ABSTRACT FROM AUTHOR]

Magnetodielectric (MD) materials have attracted considerable attention due to their intriguing physics and potential future applications. However, the intrinsicality of the MD effect is always a major concern in such materials as the MD effect may arise also due to the MR (magnetoresistance) effect. In the present case study, we report an experimental approach to analyse and separate the intrinsic and MR dominated contributions of the MD phenomenon. For this purpose, polycrystalline samples of LaGa1-xAxO3 (A = Mn/Fe) have been prepared by solid state reaction method. The purity of their structural phase (orthorhombic) has been validated by refining the X-ray diffraction data. The RTMD (room temperature MD) response has been recorded over a frequency range of 20Hz to 10MHz. In order to analyse the intrinsicality of the MD effect, FDMR (frequency dependent MR) by means of IS (impedance spectroscopy) and dc MR measurements in four probe geometry have been carried out at RT. A significant RTMD effect has been observed in selected Mn/Fe doped LaGaO3 (LGO) compositions. The mechanism of MR free/intrinsic MD effect, observed in Mn/Fe doped LGO, has been understood speculatively in terms of modified cell volume associated with the reorientation/ retransformation of spin-coupled Mn/Fe orbitals due to the application of magnetic field. The present analysis suggests that in order to justify the intrinsic/resistive origin of the MD phenomenon, FDMR measurements are more useful than measuring only dc MR or analysing the trends of magnetic field dependent change in the dielectric constant and tanδ. On the basis of the present case study, we propose that IS (FDMR) alone can be used as an effective experimental tool to detect and analyse the resistive and intrinsic parts contributing to the MD phenomenon. [ABSTRACT FROM AUTHOR]

Composition dependent Rayleigh and structural analysis was carried out on lead-free piezoceramics (1-x)Ba(Ti0.88 Sn0.12)O3-x(Ba0.7Ca0.3)TiO3 at room temperature. The system exhibits a tetragonal (P4mm) structure for x>0.21, rhombohedral (R3m) for x<0.13, and orthorhombic (Amm2) for 0.13

Composition dependent Rayleigh and structural analysis was carried out on lead-free piezoceramics (1-x)Ba(Ti0.88 Sn0.12)O3-x(Ba0.7Ca0.3)TiO3 at room temperature. The system exhibits a tetragonal (P4mm) structure for x>0.21, rhombohedral (R3m) for x<0.13, and orthorhombic (Amm2) for 0.13

The wake-up effect in yttrium doped hafnium oxide is investigated by pulse measurements, revealing the initial distribution of oxygen vacancies within symmetrical and asymmetrical layer stacks. It is shown that single pulses are sufficient to achieve a significant wake-up, whereby additional pulses lead to a stronger wake-up. Further cycling induces a degradation of the devices, which is explained by generation of oxygen vacancies and results in an electroforming step where subsequently resistive valence change mechanism switching is observed. The degradation and therefore the generation of oxygen vacancies show a strong frequency dependence, whereby the device lifetime is strongly increased for increasing frequencies. [ABSTRACT FROM AUTHOR]

The wake-up effect in yttrium doped hafnium oxide is investigated by pulse measurements, revealing the initial distribution of oxygen vacancies within symmetrical and asymmetrical layer stacks. It is shown that single pulses are sufficient to achieve a significant wake-up, whereby additional pulses lead to a stronger wake-up. Further cycling induces a degradation of the devices, which is explained by generation of oxygen vacancies and results in an electroforming step where subsequently resistive valence change mechanism switching is observed. The degradation and therefore the generation of oxygen vacancies show a strong frequency dependence, whereby the device lifetime is strongly increased for increasing frequencies. [ABSTRACT FROM AUTHOR]

We investigate the effects of Sm and La substitution in ferroelectric BiFeO3 thin films on the lattice dynamics by infrared reflection measurements at room temperature. The frequencies of the infraredactive phonon modes are studied as a function of Sm and La content in Bi1-x(Sm,La)xFeO3 composition spread films in the range from x=0 up to x=0.25, grown on SrTiO3 substrates by pulsed laser deposition. Substitution of the Bi3+ ions with small Sm3+ ions leads to the appearance of a new phase above x≈0.09 coexisting with the ferroelectric BiFeO3 phase up to x≈0.19. In contrast, for the substitution of Bi3+ ions with La3+ ions of similar size a continuous transition from the original BiFeO3 phase to a new phase takes place. In both cases, we assign the new phase to the paraelectric, orthorhombic phase. These findings are discussed in terms of the morphotropic phase boundary in Sm-doped BiFeO3 around x=0.14 with a phase coexistence, which was suggested as the origin for enhanced piezoelectric properties. [ABSTRACT FROM AUTHOR]

In this manuscript, we explore diisopropylammonium iodide (DPI) for its ferroelectric properties and phase transitions. DPI showed two phase transitions which were identified by differential scanning calorimetry and dielectric and nonlinear optical measurements. From detailed structural studies it was found that the first transition at 369K is from orthorhombic P212121 to monoclinic P21. The polar P21 phase is ferroelectric as evidenced by the pyroelectric data and has a very high value of spontaneous polarization (Ps=33 µC cm-2), which is probably the highest among other reported bulk organic ferroelectrics. The second transition at 415K is identified as polar monoclinic P21 space group to non-polar monoclinic P21/m. Thus, DPI has a high Curie temperature of 415 K. The large spontaneous polarization and high Curie temperature make DPI technologically important. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials may have potential applications in thermoelectric devices. In this work, the thermoelectric properties of orthorhombic group IV-VI monolayers AB (A=Ge and Sn; B=S and Se) are systematically investigated by the first-principles calculations and semiclassical Boltzmann transport theory. The spin-orbit coupling (SOC) is considered for their electron part, which produces observable effects on the power factor, especially for n-type doping. According to the calculated ZT, the four monolayers exhibit diverse anisotropic thermoelectric properties although they have a similar hinge-like crystal structure. The GeS along zigzag and armchair directions shows the strongest anisotropy, while SnS and SnSe show mostly isotropic efficiency of thermoelectric conversion. This can be explained by the strength of anisotropy of their respective power factor and electronic and lattice thermal conductivities. The calculated results show that the ZT between n- and p-type doping has little difference for GeS, SnS, and SnSe. It is found that GeSe, SnS, and SnSe show better thermoelectric performance compared to GeS in n-type doping and that SnS and SnSe exhibit higher efficiency of thermoelectric conversion in p-type doping. Compared to other many 2D materials, orthorhombic group IV-VI monolayers AB (A=Ge and Sn; B=S and Se) may possess better thermoelectric performance due to lower lattice thermal conductivities. Our work would be beneficial to stimulate further theoretical and experimental works. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect is observed in the 1:1:1 compound ErRhSi, which is a metamagnet is reported in this paper. ErRhSi crystallizes in the orthorhombic space group Pnma, adopting the TiNiSi structure type, with lattice parameters a(Å)=6.7903(5), b(Å)=4.1881(3), and c(Å)=7.3847(4). Our magnetic measurements confirm an antiferromagnetic phase transition at TN≈8.5K, also supported by the specific heat measurement. Crystal field effects of Er3+ are suggested by the inverse magnetic susceptibility data which do not conform to an ideal Curie-Weiss behaviour and also by the total entropy that attains Rln (2) at TN. Although the magnetic hysteresis indicates ErRhSi to be a soft magnet, several clear metamagnetic features are observed at 2K. Magnetic entropy change ΔSM=- 8.7J/kg-K is observed at about 9K with the application of 5T magnetic field. The corresponding adiabatic temperature change ΔTad is about 4K. Large magnetocaloric effects suggest that this material is suitable for the low temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

A novel material, ZrScW2PO12, with negative thermal expansion (NTE) behavior, at least from 138 to 1300 K, and intense photoluminescence (PL) property is first reported in this paper. Temperature dependent Raman and PL spectral studies indicate that the material holds an orthorhombic structure down to about 74K and exhibits NTE property in the temperature range. The intense PL covering nearly the whole visible region was observed and can be deconvoluted into four bands, which present different shifts with elevation of temperature. The abundant optical property may be attributed to n- and p-type like co-doping effect and the specific structure with the abnormal thermal expansion property of the material. The integrated properties might suggest potential applications of this material in light emitting diodes and other light emitting devices. [ABSTRACT FROM AUTHOR]

A novel material, ZrScW2PO12, with negative thermal expansion (NTE) behavior, at least from 138 to 1300 K, and intense photoluminescence (PL) property is first reported in this paper. Temperature dependent Raman and PL spectral studies indicate that the material holds an orthorhombic structure down to about 74K and exhibits NTE property in the temperature range. The intense PL covering nearly the whole visible region was observed and can be deconvoluted into four bands, which present different shifts with elevation of temperature. The abundant optical property may be attributed to n- and p-type like co-doping effect and the specific structure with the abnormal thermal expansion property of the material. The integrated properties might suggest potential applications of this material in light emitting diodes and other light emitting devices. [ABSTRACT FROM AUTHOR]

High-pressure phase of boron oxide, orthorhombic β-B2O3, has been studied in situ by synchrotron X-ray diffraction to 22 GPa and Raman scattering to 46 GPa at room temperature. The bulk modulus of β-B2O3 has been found to be 169(3) GPa that is in good agreement with our ab initio calculations. Raman and IR spectra of β-B2O3 have been measured at ambient pressure; all experimentally observed bands have been attributed to the theoretically calculated ones, and the mode assignment has been performed. Based on the data on Raman shift as a function of pressure, combined with equation-of-state data, the Gr€uneisen parameters of all experimentally observed Raman bands have been calculated. β-B2O3 enriched by 10B isotope has been synthesized, and the effect of boron isotopic substitution on Raman spectra has been studied. [ABSTRACT FROM AUTHOR]

A methodology is worked out to retrieve the numerical values of all the main parameters of the six-dimensional adiabatic potential energy surface (APES) of a polyatomic system with a quadratic T-term Jahn-Teller effect (JTE) from the ultrasound experiments. The method is based on a verified assumption that ultrasound attenuation and speed encounter anomalies when the direction of propagation and polarization of its wave of strain coincides with the characteristic directions of symmetry breaking in the JTE. For the SrF2:Cr crystal, employed as a basic example, we observed anomaly peaks in the temperature dependence of attenuation of ultrasound at frequencies of 50-160 MHz in the temperature interval of 40-60K for the wave propagating along the [110] direction, for both the longitudinal and the shear modes, the latter with two polarizations along the [001] and [1̄10] axes, respectively. We show that these anomalies are due to the ultrasound relaxation by the system of non-interacting Cr2+ JT centers with orthorhombic local distortions. The interpretation of the experimental findings is based on the T2g ⊗ (eg + t2g) JTE problem including the linear and the quadratic terms of vibronic interactions in the Hamiltonian and the same-symmetry modes reduced to one interaction mode. Combining the experimental results with a theoretical analysis, we show that on the complicated six-dimensional APES of this system with three tetragonal, four trigonal, and six orthorhombic extrema points, the latter are global minima, while the former are saddle points, and we estimate numerically all the main parameters of this surface, including the linear and quadratic vibronic coupling constants, the primary force constants, the coordinates of all the extrema points and their energies, the energy barrier between the orthorhombic minima, and the tunneling splitting of the ground vibrational states. To our knowledge, such a based-on-experimental-data numerical reconstruction of the APES of a JTE problem in the five-dimensional space of all active tetragonal and trigonal displacements has not been reported before. [ABSTRACT FROM AUTHOR]

In this paper we provide an accurate high-pressure structural and optical study of the MAPbI3 hybrid perovskite. Structural data show the presence of a phase transition toward an orthorhombic structure around 0.3 GPa followed by full amorphization of the system above 3 GPa. After releasing the pressure, the system keeps the high-pressure orthorhombic phase. The occurrence of these structural transitions is further confirmed by pressure induced variations of the photoluminescence signal at high pressure. These variations clearly indicate that the bandgap value and the electronic structure of MAPI change across the phase transition. [ABSTRACT FROM AUTHOR]

Polycrystalline β-PbO films were grown by pulsed laser deposition in atmospheres ranging from oxygen-poor (the oxygen pressure of 0.01 Pa) to oxygen-rich (13 Pa) conditions, and the oxygen chemical potential was further enhanced by ozone annealing to examine hole doping. It was found that each of the as-grown β-PbO films showed poor electrical conductivity, σ?7.1?×?10² S cm-1) but it is the result of the formation of an n-type PbO2 phase because oxygen chemical potential exceeded the phase boundary limit. The striking difference in carrier generation between PbO and SnO is discussed based on the electronic structures calculated by density functional theory. [ABSTRACT FROM AUTHOR]

X-ray powder diffraction and Raman scattering of LiTaO3 (LT) and (Li,Mg)TaO3 (LMT) have been measured under pressure up to 46 GPa. Above 30 GPa, the ferroelectric rhombohedral phase (R3c, Z = 6) of LiTaO3 transforms to a paraelectric orthorhombic phase (Pnma with Z = 4) with a large hysteresis. Rietveld profile fitting analysis shows that the Li-O bond is compressed and approaches that of Ta-O with pressure. The cation distribution analysis of the orthorhombic perovskite structure shows that Li and Ta are located in the octahedral 8-fold coordination sites. Difference Fourier ∣Fobs(hkl)∣ - ∣Fcal(hkl)∣ maps of LiTaO3 and (Li,Mg)TaO3 indicate polarization in the c axis direction and a more distinct electron density distribution around the Ta position for (Li,Mg)TaO3 compared to LiTaO3. The observed effective charges indicate that for (Li,Mg)TaO3 without vacancies Ta5+ becomes less ionized as a function of Mg substitution. Considering both site occupancy and effective charge analysis, Ta5+ is reduced to Ta4.13+. Mg2+ and O2- change to Mg1.643+ and O1.732 -, respectively. The space- and time-averaged structures of the dynamical vibration of atoms can be elucidated from the electron density analysis by difference Fourier and temperature factors T(hkl) in the structure refinement. The refinement of the temperature factor is consistent with the cation distribution assuming full stoichiometry. The residual electron density induced from the excess electron in (Li,Mg)TaO3 indicates more electrons around the Ta site, as confirmed by the effective charge analysis. Raman spectra of LiTaO3 and (Li,Mg)TaO3 show notable changes over the measured pressure range. Raman peaks centered at 250 cm-1 and 350 cm-1 at ambient pressure merge above 8 GPa, which we associate with the diminishing of difference in distances between Li-O and Ta-O bonds with pressure in both materials. Raman spectra show significant changes at 28 GPa and 33 GPa for LT and LMT, respectively, due to the structural transition from R3c to Pnma consistent with the x-ray diffraction results. [ABSTRACT FROM AUTHOR]

Despite wide studies of Na0.5Bi0.5TiO3, structure of this material and its connection with the observed physical properties still raise numerous questions due to mutually contradicting results obtained. Here, structure and dielectric properties of poled and unpoled Na0.5Bi0.5TiO3-CaTiO3 solid solutions are studied, projecting the obtained concentration dependence of structure and dielectric properties on pure Na0.5Bi0.5TiO3 as the end member of this material group. X-ray diffraction patterns for Na0.5Bi0.5TiO3-CaTiO3 solid solutions reveal dominating of an orthorhombic Pnma phase, even for the compositions approaching the end composition (Na0.5Bi0.5TiO3), whereas structure of pure Na0.5Bi0.5TiO3 can be considered, assuming coexistence of rhombohedral and orthorhombic phases. This allows one to avoid appearance of a large difference of rhombohedral distortions between the unpoled and poled Na0.5Bi0.5TiO3, if the rhombohedral distortion is calculated as for single R3c phase. Features of dielectric permittivity, corresponding to the observed structural phase transition, are identified. It is discussed that the rhombohedral R3c phase is responsible for appearance of the frequency-dependent shoulder of dielectric permittivity temperature dependence, characteristic for unpoled Na0.5Bi0.5TiO3. [ABSTRACT FROM AUTHOR]

X-ray powder diffraction and Raman scattering of LiTaO3 (LT) and (Li,Mg)TaO3 (LMT) have been measured under pressure up to 46 GPa. Above 30 GPa, the ferroelectric rhombohedral phase (R3c, Z = 6) of LiTaO3 transforms to a paraelectric orthorhombic phase (Pnma with Z = 4) with a large hysteresis. Rietveld profile fitting analysis shows that the Li-O bond is compressed and approaches that of Ta-O with pressure. The cation distribution analysis of the orthorhombic perovskite structure shows that Li and Ta are located in the octahedral 8-fold coordination sites. Difference Fourier ∣Fobs(hkl)∣ - ∣Fcal(hkl)∣ maps of LiTaO3 and (Li,Mg)TaO3 indicate polarization in the c axis direction and a more distinct electron density distribution around the Ta position for (Li,Mg)TaO3 compared to LiTaO3. The observed effective charges indicate that for (Li,Mg)TaO3 without vacancies Ta5+ becomes less ionized as a function of Mg substitution. Considering both site occupancy and effective charge analysis, Ta5+ is reduced to Ta4.13+. Mg2+ and O2- change to Mg1.643+ and O1.732 -, respectively. The space- and time-averaged structures of the dynamical vibration of atoms can be elucidated from the electron density analysis by difference Fourier and temperature factors T(hkl) in the structure refinement. The refinement of the temperature factor is consistent with the cation distribution assuming full stoichiometry. The residual electron density induced from the excess electron in (Li,Mg)TaO3 indicates more electrons around the Ta site, as confirmed by the effective charge analysis. Raman spectra of LiTaO3 and (Li,Mg)TaO3 show notable changes over the measured pressure range. Raman peaks centered at 250 cm-1 and 350 cm-1 at ambient pressure merge above 8 GPa, which we associate with the diminishing of difference in distances between Li-O and Ta-O bonds with pressure in both materials. Raman spectra show significant changes at 28 GPa and 33 GPa for LT and LMT, respectively, due to the structural transition from R3c to Pnma consistent with the x-ray diffraction results. [ABSTRACT FROM AUTHOR]

We report the magnetic properties, of nano-crystalline powders Tb1-xYxMnO3 (x=0, 0.1, 0.2, 0.3 and 0.4), as perceived by neutron diffraction, and elucidate the effect of Tb site substitution on the magnetic structure of TbMnO3. All samples crystallized in the orthorhombic structure conforming to space group Pnma, and exhibited an incommensurate collinear antiferromagnetic ordering of the Mn ions below ~40 K. Furthermore, at T≤20 K, all these samples showed a change in magnetic structure (of Mn moments) to a spiral ordering down to 2K, the lowest measured temperature. For the samples with x=0, 0.1, and 0.2, a short-ranged two dimensional (2D) ordering of Tb moments was also observed at 2K. However, for the other samples (x=0.3 and 0.4), no magnetic ordering of Tb moments was found down to 2K. So with Y substitution, a crossover from 2D ordering to a disordering of Tb moments was observed. The moments at the Mn site were found to be lower than the full Mn3+ (4µB) moment for all the samples below 40 K. The magnetic properties of all the samples studied by us in nano form are more pronounced than those of the reported single crystals of same compositions [V. Yu. Ivanov et al., JETP Lett. 91, 392-397 (2010)]. [ABSTRACT FROM AUTHOR]

We report the magnetic properties, of nano-crystalline powders Tb1-xYxMnO3 (x=0, 0.1, 0.2, 0.3 and 0.4), as perceived by neutron diffraction, and elucidate the effect of Tb site substitution on the magnetic structure of TbMnO3. All samples crystallized in the orthorhombic structure conforming to space group Pnma, and exhibited an incommensurate collinear antiferromagnetic ordering of the Mn ions below ~40 K. Furthermore, at T≤20 K, all these samples showed a change in magnetic structure (of Mn moments) to a spiral ordering down to 2K, the lowest measured temperature. For the samples with x=0, 0.1, and 0.2, a short-ranged two dimensional (2D) ordering of Tb moments was also observed at 2K. However, for the other samples (x=0.3 and 0.4), no magnetic ordering of Tb moments was found down to 2K. So with Y substitution, a crossover from 2D ordering to a disordering of Tb moments was observed. The moments at the Mn site were found to be lower than the full Mn3+ (4µB) moment for all the samples below 40 K. The magnetic properties of all the samples studied by us in nano form are more pronounced than those of the reported single crystals of same compositions [V. Yu. Ivanov et al., JETP Lett. 91, 392-397 (2010)]. [ABSTRACT FROM AUTHOR]

We investigate the structural, magnetic, and magnetodielectric properties of DyMn0.5Cr0.5O3. The sample can be indexed with an orthorhombic phase with B site disordered space group Pbnm. The valence state of both Mn and Cr ions are suggested to be +3 based on the results of x-ray photoelectron spectroscopy. Two thermally excited dielectric relaxation at temperatures TN2

We investigate the structural, magnetic, and magnetodielectric properties of DyMn0.5Cr0.5O3. The sample can be indexed with an orthorhombic phase with B site disordered space group Pbnm. The valence state of both Mn and Cr ions are suggested to be +3 based on the results of x-ray photoelectron spectroscopy. Two thermally excited dielectric relaxation at temperatures TN23+/Cr3+ ions associated with electron hopping between them are observed. The absence of any noticeable magnetoresistance effect (MR<0.5%) demonstrates that the observed magnetodielectric effect is an intrinsic behavior. These results suggest that DyMn0.5Cr0.5O3 is a magnetodielectric compound, whose dielectric properties are dependence of the applied magnetic field, which exhibits such effects near room temperature and holds great promise for future device applications. [ABSTRACT FROM AUTHOR]