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NiCr2O4 nanoparticles with average particle size ∼15 nm, a single-domain size maintains the bulk canted antiferromagnetic ground state, were synthesized by a microwave combustion method. The magnetic behavior was carefully investigated by static and dynamic magnetic susceptibility measurements. In addition to a spin-glass-like behavior below paramagnetic-ferrimagnetic transition at T C, the NiCr2O4 nanoparticles demonstrate a low-temperature cluster spin glass transition below the spin canting transition T S, which manifests itself as a magnetic anomaly peak around ∼12 K (at 100 Oe) in the zero-field cooled magnetization with a relatively stronger field dependence in a 'de Almeida-Thouless' line for spin glasses. The AC susceptibility analyses in different approaches demonstrate a larger relative peak temperature variation per frequency decade and a longer characteristic relaxation time in the order of 0.04 and 10−7 s, against 0.01 and 10−9 s for the high-temperature blocking, indicating the slow spin dynamics for the low-temperature cluster glassy phase. A field-temperature magnetic phase diagram is proposed for the single-domain NiCr2O4 nanoparticles. [ABSTRACT FROM AUTHOR]

Superconductivity is caused by electron pairs that are canonically isotropic, whereas some exotic superconductors are known to exhibit non-trivial anisotropy stemming from unconventional pairings. However, superconductors with hexagonal symmetry, the highest rotational symmetry allowed in crystals, exceptionally have strong constraint that is called emergent rotational symmetry (ERS): anisotropic properties should be very weak especially near the critical temperature Tc even for unconventional pairings such as d-wave states. Here, we investigate superconducting anisotropy of the recently-found hexagonal Kagome superconductor CsV3Sb5, which is known to exhibit various intriguing phenomena originating from its undistorted Kagome lattice formed by vanadium atoms. Based on calorimetry performed under accurate two-axis field-direction control, we discover a combination of six-and two-fold anisotropies in the in-plane upper critical field. Both anisotropies, robust up to very close to Tc, are beyond predictions of standard theories. We infer that this clear ERS violation with nematicity is best explained by multi-component nematic superconducting order parameter in CsV3Sb5 intertwined with symmetry breakings caused by the underlying charge-density-wave order. [ABSTRACT FROM AUTHOR]

The table-like behavior of the magnetic entropy change is generally observed in rare-earth-based alloys (e.g. La(Fe,Si)13, Gd50Co45Fe5, Gd56Ni15Al27Zr2, Gd (1 − x − y) Co x Al y etc). Here, we report similar table-like behavior in a bulk perovskite Eu0.5Sr0.5MnO3–EuMnO3 composite system with a working temperature span of ∼80 K for a field change of ∼70 kOe. AC susceptibility and time-dependent DC magnetization relaxation measurements confirm the presence of interacting ferromagnetic clusters with a Vogel–Fulcher freezing temperature of T 0 ∼ 42.7 K. The Langevin function fittings of the isothermal magnetization curves show a non-monotonous variation of cluster size with temperature. We propose a model for the high-field dependency of the ferromagnetic cluster coupling in the composite system. This widens the transition temperature region of long-range order formation and hence gives rise to the table-like magnetocaloric effect in Eu0.5Sr0.5MnO3–EuMnO3 composite systems. [ABSTRACT FROM AUTHOR]

Oxide superconductor is one of the most important forms of unconventional superconductors, in which the transition temperatures of thallium series, mercury series and copper-carbon series superconductors can reach 110 K or above. High superconducting transition temperature and irreversible magnetic field in liquid nitrogen temperature region have attracted much attention. Obviously, the high superconducting critical temperature increases the choice of cooling medium for superconducting applications. Economical and practical coolants are expected to expand the application fields of these high superconducting transition temperature (Tc) superconductors and increase the feasibility of long-term operation. In this paper, the development and superconducting properties of 110 K superconducting materials including thallium, mercury and copper-carbon superconductors are introduced and summarized, and the factors affecting the superconducting transition temperature are analyzed theoretically to qualitatively explain the reasons for the high Tc of high temperature superconductors. Special attention is paid to the analysis of the differences of their irreversible fields, and the possible new applications of these high critical temperature superconductors are prospected. [ABSTRACT FROM AUTHOR]

The content of transition‐metal ions and their valence state for three compositions of NixCuyMn3−x−yBO5 are estimated by the methods of X‐ray absorption spectroscopy. In all the three compositions, the copper content does not exceed 0.25. One of the compositions has manganese ions both in the trivalent and bivalent states according to the K‐edge position. The calculations of the total energies of various cation‐ordered structures using the software package Wien2K show that copper ions predominately occupy one site, namely, 2(2d). The measurements of the magnetic properties show two types of magnetic transitions in all the three compositions, with one of them being in the range of 60–75 K and the other one at 10 K. Based on the exchange interactions calculated in the framework of the empirical model, magnetic ordering temperatures are estimated for two‐ and three‐sublattice structures and the magnetic transition in the range of 60–75 K is supposed to be connected with magnetic moment ordering in sites 2 and 3. [ABSTRACT FROM AUTHOR]

The investigations of the crystal structure, magnetic and electronic properties of Co3BO5 at high temperatures were carried out using powder X-ray diffraction, magnetic susceptibility, electrical resistivity, and thermopower measurements. The orthorhombic symmetry (Sp.gr. Pbam) was observed at 300 K and no evidence of structural phase transitions was found up to 1000 K. The compound shows a strong anisotropy of the thermal expansion. A large negative thermal expansion along the a-axis is observed over a wide temperature range (T = 300–600 K) with αa = −35 M K−1 at T = 500 K with simultaneous expansion along the b- and c-axes with αb = 70 M K−1 and αc = 110 M K−1, respectively. The mechanisms of thermal expansion are explored by structural analysis. The activation energy of the conductivity decreases significantly above 700 K. Electronic transport was found to be a dominant conduction mechanism in the entire temperature range. The correlations between the thermal expansion, electrical resistivity, and effective magnetic moment were revealed and attributed to the evolution of the spin state of Co3+ ions towards the spin crossover and gradual charge-ordering transition. [ABSTRACT FROM AUTHOR]

A safe, three-step reaction sequence to [1,3]-dithiolo-[4,5- d ][1,3-dithiole]-2,5-dione starting from carbon disulfide is presented. Optimized reaction conditions, rigorous purification, and full characterization of all intermediates provide reproducibly a final product of superior quality with a melting point of 181 °C (dec.). [ABSTRACT FROM AUTHOR]

Within the cuprate constellation, one fixed star has been the superconducting dome in the quantum phase diagram of transition temperature vs. the excess charge on the Cu in the CuO2 -planes, p, resulting from O-doping or cation substitution. However, a more extensive search of the literature shows that the loss of the superconductivity in favor of a normal Fermi liquid on the overdoped side should not be assumed. Many experimental results from cuprates prepared by high-pressure oxygenation show Tc converging to a fixed value or continuing to slowly increase past the upper limit of the dome of p = 0.26–0.27, up to the maximum amounts of excess oxygen corresponding to p values of 0.3 to > 0.6. These reports have been met with disinterest or disregard. Our review shows that dome-breaking trends for Tc are, in fact, the result of careful, accurate experimental work on a large number of compounds. This behavior most likely mandates a revision of the theoretical basis for high-temperature superconductivity. That excess O atoms located in specific, metastable sites in the crystal, attainable only with extreme O chemical activity under HPO conditions, cause such a radical extension of the superconductivity points to a much more substantial role for the lattice in terms of internal chemistry and bonding. [ABSTRACT FROM AUTHOR]

The ludwigite Co2FeBO5 has been studied experimentally using 57Fe Mössbauer spectroscopy and theoretically using DFT + GGA calculations. The room-temperature Mössbauer spectra are composed of four quadrupole doublets corresponding to the high-spin Fe3+ ions in octahedral oxygen coordination. All components undergo splitting below 117 K due to the magnetic hyperfine fields. The DFT + GGA calculations performed for three models of Fe ion distributions have revealed that the ground state corresponds to the "Fe4(HS)" model with the high-spin Fe3+ ions located at the M4 site and the high-spin Co2+ ions located at the M1, M2, and M3 sites. A ferrimagnetic ground state, with the Co and Fe magnetic moments being nearly parallel to the b-axis and a total magnetic moment of circa 1.1μB f.u.−1, was found. The other Fe distributions cause an increase in the local octahedral distortions and transformation of the spin state. The calculated quadrupole splitting values are in good agreement with the experimental values obtained by Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

We report spin-driven multiferroicity above 100 K in the ludwigite Cu(II) oxyborate Cu2CrBO5. Spontaneous polarization, which reaches 35 μC m−2 at 5 K, appears below 120 K, concomitantly with an incommensurate antiferromagnetic order and complex magnetodielectric effects. In magnetically induced ferroelectrics, multiferroicity usually appears at low temperature because of the competing magnetic exchanges needed to stabilize a magnetic spiral. The remarkably high transition temperature observed in Cu2CrBO5 originates from the presence of strong Cu–O–Cu magnetic super-exchange interactions, which are not weakened by Cu/Cr cationic disorder. Our result provides an important contribution to the search for high temperature spin-driven multiferroics among low-dimensional cuprates. [ABSTRACT FROM AUTHOR]

Novel effects induced by nonmagnetic impurities in frustrated magnets and quantum spin liquid represent a highly nontrivial and interesting problem. A theoretical proposal of extended modulated spin structures induced by doping of such magnets, distinct from the well-known skyrmions has attracted significant interest. Here, we demonstrate that nonmagnetic impurities can produce such extended spin structures in h-YMnO3, a triangular antiferromagnet with noncollinear magnetic order. Using inelastic neutron scattering (INS), we measured the full dynamical structure factor in Al-doped h-YMnO3 and confirmed the presence of magnon damping with a clear momentum dependence. Our theoretical calculations can reproduce the key features of the INS data, supporting the formation of the proposed spin textures. As such, our study provides the first experimental confirmation of the impurity-induced spin textures. It offers new insights and understanding of the impurity effects in a broad class of noncollinear magnetic systems. In geometrically frustrated magnets small perturbations, such as non-magnetic impurities, can significantly alter the ground state. Here, using inelastic neutron scattering, Park et al. explore such a situation in Al-doped h-YMnO3, where the Aluminum dopants induce an extended spin structure. [ABSTRACT FROM AUTHOR]

The ability of cobalt to take, depending on the temperature, pressure, and doping, various charge and spin states in oxide compounds periodically becomes the topic of scientific controversy and is a frequent cause of ambiguity in the interpretation of experimental results. In this review, we will discuss cobaltites, i.e., oxide compounds of cobalt, in which cobalt is in an oxidation state (charge state) of 3+. In these compounds, Co3+ ions can take the following spin configurations: high-spin, low-spin, and intermediate-spin configurations. The conditions for the formation of various spin states are given on the basis of the Tanabe–Sugano diagrams. It is shown how X-ray spectral methods, such as X-ray photoelectron spectroscopy, X-ray emission spectroscopy, X-ray absorption spectroscopy, and X-ray magnetic dichroism, can be used to study cobaltites. By using Co L2,3 X-ray absorption spectra that have a rich structure, one can determine the charge and spin states of cobalt ions. These spectra can be reproduced by atom-like multiplet calculations that involve many electrons and use the energy splitting of atomic orbitals by the ligand field as a free parameter. Absorption K spectra of oxygen are of a band nature, i.e., these spectra can be used, by mixing the 3d states of cobalt with the 2p states of oxygen, to estimate the spin state of cobalt ions and to analyze cobaltite phases after external influences. It is shown that the spin states of cobalt ions can be determined from Co Kβ X‑ray emission spectra (electronic transition ) that are sensitive to the spin state of 3d electrons because of the strong exchange interaction between the 3p hole and 3d orbitals in the final state of the emission process. A classic example of cobaltites with a low-spin configuration of cobalt ions is lithium cobaltite LiCoO2 that is a well-known material for power source cathodes. The nature of holes in defective cobaltites of the LixCoO2 (x < 1) type is considered. It is shown that holes arising from defects in the lithium sublattice are of an oxygen nature. In cobaltite LaCoO3 that also contains trivalent cobalt ions, a transition from a low-spin state to a high-spin state occurs at temperatures above 90 K. The feasibility of an intermediate-spin state in this compound is also considered. The results of X-ray spectral studies of double substitution perovskites Ln1 –xAxCo1 –yMyO3 (Ln is a lanthanide, A is Ca or Sr, and M is a transition element) are given, and changes in the charge states of cobalt ions upon doping of perovskites are shown. The results of experimental determination of spin states in octahedrons and pyramids of cobaltites LnBaCo2O6 – δ () at temperatures below and above the temperature of the metal-insulator transition are systematized. Methods for determining spin states on the basis of X-ray spectral data are discussed. It is shown in the last section of the article how the charge state and concentration of cobalt ions in doped layered cobaltites LnBaCo4O7 can be determined using X-ray absorption spectroscopy. In these compounds, cobalt ions are in tetrahedral positions and, consequently, trivalent cobalt ions should be exclusively in the high-spin state. [ABSTRACT FROM AUTHOR]

In this work, we report the successful synthesis of a polycrystalline, binary compound ErIr3, forming a macroscopic coexistence of two different cubic structures (AuBe5-type and AuCu3-type). The magnetic properties of two polymorphs could be distinguished by means of different measurement techniques. The detailed study of dc magnetization and heat capacity behaviour confirm that the phase with the cubic AuBe5-type structure orders ferromagnetically below 5.2 K, while the AuCu3-type phase remains paramagnetic down to 2.5 K. The presence of a glassy state in this compound is manifested in the frequency dependent ac susceptibility measurement, magnetic relaxation and magnetic memory effect. [ABSTRACT FROM AUTHOR]

Ni2In-type MnMX alloys possess interesting noncollinear magnetic structures that may embed a variety of physical phenomena. In this work, magnetic and electrical transport properties of pure Ni2In-type structure Mn1 +xCu1−xGa (x = 0.3–0.5) alloys are investigated systematically. A cluster spin-glass phase is identified below the Curie temperature by magnetization and ac susceptibility measurements in x = 0.5 sample. Mediated by the exchange interaction between Mn-Mn clusters, significant exchange bias effect and coercivity are established, in which a giant exchange bias field of up to 0.323 T is observed in x = 0.5 sample. The exchange bias effect and coercivity, as well as the anomalous Hall effect are found to be greatly tuned via field cooling process. The large EB and coercivity identified in Mn–Cu–Ga alloys make them potentially applied in rare-earth-free magnets and spintronic devices. [ABSTRACT FROM AUTHOR]

In a superconductor that lacks inversion symmetry, the spatial part of the Cooper pair wave function has a reduced symmetry, allowing for the mixing of spin-singlet and spin-triplet Cooper pairing channels and thus providing a pathway to a non-trivial superconducting state. Materials with a non-centrosymmetric crystal structure and with strong spin–orbit coupling are a platform to realize these possibilities. Here, we report the synthesis and characterisation of high quality crystals of Sn4As3, with non-centrosymmetric unit cell (R3m). We have characterised the normal and superconducting states using a range of methods. Angle-resolved photoemission spectroscopy shows a multiband Fermi surface and the presence of two surface states, confirmed by density-functional theory calculations. Specific heat measurements reveal a superconducting critical temperature of Tc ∼ 1.14 K and an upper critical magnetic field of μ0Hc ≳ 7 mT, which are both confirmed by ultra-low temperature scanning tunneling microscopy and spectroscopy. Scanning tunneling spectroscopy shows a fully formed superconducting gap, consistent with conventional s-wave superconductivity. [ABSTRACT FROM AUTHOR]

An Fe3BO5 anode material synthesized by reducing Fe3BO6 was comprehensively studied for use in both lithium- and sodium-ion batteries. As a lithium-ion battery anode, the obtained Fe3BO5 displays a high initial reversible capacity of 654.7 mA h g−1 (with a coulombic efficiency of 75%) at a current density of 0.1 A g−1 and a favorable cycling performance, with a capacity of 544.6 mA h g−1 at 0.4 A g−1 after 400 cycles. As a sodium-ion battery anode, Fe3BO5 displays initial discharge/charge capacities of 644.6 and 433.6 mA h g−1 at a current density of 0.1 A g−1. Besides this, Fe3BO5 exhibits a stable reversible capacity of about 380 mA h g−1 at 0.4 A g−1 during the first 100 cycles and an excellent rate performance with a high capacity of 304.5 mA h g−1, even at a current density of as large as 4 A g−1. Kinetics analysis shows that the significance in high Na+ capacitive contribution at a high rate should account for the excellent rate performance. The excellent electrochemical properties demonstrate that the Fe3BO5 material could be an effective and promising anode candidate for both lithium- and sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Delafossite mixed metal oxides of the form BaCuO2 and BaCu1M1−xO2 (M = Ni, Fe and Co) were successfully synthesized following a sol–gel citrate method. The products, obtained after heat treatment under N2 at 800 °C, were characterized using several techniques such as: thermogravimetric analysis (TG), inductively coupled plasma atomic emission spectroscopy (ICP), X-ray diffraction (XRD) spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectroscopy and temperature-programmed reduction (TPR). The formation of the delafossite oxide structure for all solid powders was confirmed by XRD. The BET surface area of all catalysts was lower than 10 m2 g−1. The catalytic performance of the synthesized catalysts was evaluated in the vapor-phase hydrogenation of benzaldehyde. Benzyl alcohol and toluene were obtained through consecutive hydrogenation/hydrogenolysis reactions, while benzene was formed via a concomitant hydrogenolysis reaction. BaCuO.47Ni0.51O2 catalyst showed better activity at 250 °C with 98% benzaldehyde conversion. Under the same conditions, BaCuO.52Fe0.48O2 catalyst showed the highest selectivity for benzyl alcohol (84% at 20% of conversion). [ABSTRACT FROM AUTHOR]

A comparative analysis of the copper and iron ions bonds exchange energies was conducted for various variants of orderings and distributions of iron ions among crystallographic positions in ludwigite Cu2FeBO5. Analysis showed that the exchange bonds of iron ions play a key role in the formation of magnetic order. The magnetic ordering strongly depends on the distribution of iron ions among the positions. In the case when the Fe3+ is in the same position as in Fe3BO5, the most favorable magnetic structure is similar to the magnetic structure of ludwigite Fe3BO5. In other cases, the type of magnetic ordering is different. [ABSTRACT FROM AUTHOR]

The parameters of the Mössbauer spectra on 67Cu(67Zn), 67Ga(67Zn) isotopes, and the data of nuclear quadrupole resonance on an 17O isotope are anlayzed, and the lattice gradient of the electric field for the crystal lattice YBa2Cu3O7 is calculated. It is shown that these parameters correspond to the model when the hole is predominantly in the sublattice of the oxygen chain. [ABSTRACT FROM AUTHOR]

The conditions for the occurrence of reentrant superconductivity in granular superconductors are studied. The parameters of synthesis of the ceramic samples of CaLaBaCuO, SrLaBaCuO and YBaSrCuOSe compositions, the results of their microstructure research, the elemental composition and the temperature dependence of the resistance are given. Samples are obtained, which reproducibly exhibit the reentrant superconductivity after the tens of thermal cycling. The relationship between the occurrence of reentrant superconductivity and the oxygen content in the samples was not established. [ABSTRACT FROM AUTHOR]

Ludwigites is a type of oxyborates compounds with BO3 groups, which have low-dimensional elements: stairs, zigzag walls, tapes. Such structural features influence on the physical properties of the compounds and cause charge ordering, the existence of two magnetic subsystems, ordered at different temperatures in the perpendicular direction, the quasi-one-dimensional magnetism, spin-glass state. In this survey, we have summarized all known experimental and theoretical studies and analyzed the proposed by the authors mechanisms of phase transitions in the ludwigite structure oxyborates. [ABSTRACT FROM AUTHOR]

The results of recent studies are discussed in which first principles calculations at the atomic level have been used to expand the thermodynamic database for science-based predictive modeling of the chemistry, composition and structure of unwanted oxides that deposit on the fuel rods in pressurized light water nuclear reactors. Issues discussed include the origin of the particles that make up deposits, the structure and properties of the deposits, and the forms by which boron uptake into the deposits can occur. These first principles approaches have implications for other research areas, such as hydrothermal synthesis and the stability and corrosion resistance of other materials under other extreme conditions. [ABSTRACT FROM AUTHOR]

In an attempt to search for mixed alkaline-earth and transition metal pyroborates, the title compound, barium manganese(II) pyroborate, has been synthesized by employing a flux method. The structure of BaMnB2O5 is composed of MnO5 square pyramids that form Mn2O8 dimers by edge-sharing and of pyroborate units ([B2O5]4-) that are composed of two corner-sharing trigonal-planar BO3 units. These building blocks share corners to form ∞ 2[MnB2O5]2- layers extending parallel to (100). The Ba2+ cations reside in the gap between two manganese pyroborate slabs with a coordination number of nine. The title compound forms an interesting spiral framework propagating along the 21 screw axis. The structure is characterized by two alternating layers, which is relatively rare among known transition-metal-based pyroborate compounds. [ABSTRACT FROM AUTHOR]

A complex [Er(hfac)3[NITPh-p-Cl]2], (hfac=hexafluoroacetylacetonate; and NITPh-p-Cl=2-(4′-chlorophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was synthesized and characterized structurally by X-ray crystal structure and magnetic measurements. X-ray crystal structure analysis revealed that the Er(III) ions are eight-coordinated and the complex has slightly distorted dodecahedron geometry. The variable temperature magnetic susceptibility measurements studies revealed that there are antiferromagnetic interactions between the Er(III) ions and the radicals in this complex. [ABSTRACT FROM PUBLISHER]

In this investigation, we explore a facile synthesis of Fe3BO6 in the form of small crystallites in the specific shape of nanotubes crystallized from a supercooled liquid Fe2O3-B2O3 precursor. This study includes high resolution transmission electron microscopy (HRTEM) images, magnetic, optical, and impedance properties of the sample. HRTEM images reveal small tubes of Fe3BO6 of 20 nm diameter. A well resolved hysteresis loop appears at 5 K in which the magnetization does not saturate even up to as high field as 50 kOe. It means that the Fe3BO6 nanotubes behave as highly antiferromagnetic in nature in which the surface spins do not align along the field so easily. The temperature dependent impedance describes an ionic Fe3BO6 conductor with a reasonably small activation energy Ea ∼ 0.33 eV. Impedance formalism in terms of a Cole-Cole plot shows a deviation from an ideal Debye-like behavior. We have also reported that electronic absorption spectra are over a spectral range 200–800 nm of wavelengths in order to find out how a bonded surface layer present on the Fe3BO6 crystallites tunes the 3d → 3d electronic transitions in Fe3+ ions. [ABSTRACT FROM AUTHOR]

The magnetic properties of molecular nanomagnets Mn -Ac (acetate) through Ising model are studied by using the Monte Carlo simulations. The effect of exchange interactions are studied in the molecular nanomagnets Mn -Ac. The reduced exchange interaction versus the reduced exchange interaction and external magnetic field in Mn -Ac shell-core structure is given. The reduced exchange interaction in shell-core versus the crystal field is studied. The effect of external magnetic in the crystal field is established. The blocking temperature is given for different values of crystal field and for temperature T = 1.0 K. The total magnetization versus crystal field and external magnetic field is given for different temperatures. The magnetic coercive field is given for different values of crystal field. [ABSTRACT FROM AUTHOR]

In the present manuscript, we have studied the structural and magnetic properties of CoFeO nanoparticles synthesized at different pH levels (7, 10 and 12) via co-precipitation method. The structural analysis of the samples indicates the structural distortion at the octahedral site which has been found correlated with the observed roomtemperature magnetic moment of the CoFeO nanoparticles. Magnetic studies reveal multiple magnetic phases and surface spin disorder in the samples. Spin canting/glass behaviour is also observed in the as-synthesized CoFeO nanoparticles. In addition to these, the as-synthesized samples also show a novel metamagnetic transition due to the coexistence of antiferromagnetic and ferromagnetic ordering, simultaneously. The coexistence of antiferromagnetic and ferromagnetic phases is attributed to spin canting/surface spin disorder in the nanocrystalline samples. Mossbauer data also supports the presence of spin canting in the samples. [ABSTRACT FROM AUTHOR]

We propose an S S I S S junction model to describe the intergrain junctions of compounds with intrinsic mixtures of two superconductor phases. Considering the polycrystalline compound Hg,Re-1223 as a representative case, fitting using this model of a junction in J as a function of applied magnetic field μ H proves to be better than a simple SIS junction model for μ H > 1.0 mT and T≈ T. [ABSTRACT FROM AUTHOR]

Magnetic properties of the ZnNiFeO nanoparticle were investigated by measuring the dc magnetization and ac susceptibility. The ferrimagnetic phase forms below 225 K. Through analyzing the relationship between the transition temperature and frequency in the ac susceptibility, it is confirmed that the magnetic dipolar interaction between ferrimagnetic nanoparticles causes a cluster-glass behavior. In the low-temperature region (below 90 K), an antiferromagnetic phase is found to coexist with the ferrimagnetic phase. The antiferromagnetic interaction between the B-site Fe ions plays an important role in the formation of the antiferromagnetic phase. [ABSTRACT FROM AUTHOR]

We have studied harmonic generation in the ultra-weak magnetic fields of bulk sample of the HgBaCa Cu Opolycrystalline superconductor. Dependence of the odd and even harmonics on the dc magnetic field, amplitude of the ac magnetic field, and the temperature was investigated. We observe very high-order odd harmonics generation when H=0. When dc field H≠0 is applied, even harmonics also appear and shape of the odd harmonics does not change. Our experiments show that the amplitudes of the odd harmonics squarely depend on the magnitude of the dc field. Numerical results of our experiments have demonstrated that the $J_{c}=J_{c}(0)H_{0}^{2}/\left (H+H_{0}^{2}\right )$ critical-state theoretical model is preferable for investigating the sample. [ABSTRACT FROM AUTHOR]

The series of BaBi Pb O(0 ≤ y≤1) has been synthesized by high-temperature solid-state reaction. X-ray and selected area electron diffraction data indicate that BaBi Pb O(0 ≤ y≤ 0.88) crystallizes in space group P1 and BaBi Pb O (0.93 ≤ y≤1) crystallizes in space group Imma. The samples with the nominal formula BaBi Pb O( y = 0.70, 0.80, 0.90) shows superconductivity with transition temperature ( T) around 11 K. When BaBi Pb O (0 ≤ y≤0.80) was treated with KOH and KF at 450 C, the corresponding samples with the nominal formula Ba KBi Pb O (0 ≤ y≤ 0.80) were obtained, which shows superconductivity with T changing from 30 to 11 K. [ABSTRACT FROM AUTHOR]

Superconducting samples of the type (ZnFeO)GdBaCuO were synthesized by the conventional solid-state reaction technique. The nanosized (ZnFeO) content x varied from 0 to 0.1 wt% of the samples' total mass. The prepared samples were characterized using X-ray powder diffraction (XRD) and scanning and transmission electron microscopes (SEM and TEM). The effect of ZnFeO addition, which acts as flux pinning centers, was investigated using ac magnetization at different applied dc magnetic fields. It was found that addition of the nanosized (ZnFeO) up to 0.06 wt% enhances the critical current density J and the superconducting transition temperature T. On the other hand, the superconducting properties of these samples are deteriorated for x > 0.06 wt%. The irreversibility line was thermally activated. The logarithmic plot of H versus (1 − T/ T(0)) shows a crossover at about 500 Oe, reflecting the transition from two- to three-dimensional vortex fluctuations. The B- T curves are well fitted according to Matsushita's model, which is based on the de-pinning mechanism caused by thermally activated flux creep. [ABSTRACT FROM AUTHOR]

Novel manganese and boron containing nanomaterials have been investigated for applications in rechargeable lithium ion batteries (LIBs) in recent years owing since they are more environmentally-benign and more abundant in nature than the materials currently employed. In this study, one-dimensional (1D) MnBOOH nanorods and MnBOOH nanorod bundles were controllably fabricated by using NHHBO and Mn(NO) as reagents via a hydrothermal or solvothermal process, respectively, without any surfactants or templates at 220 °C. It is interesting to find that both materials are transformed into MnOBO nanorods/nanorod bundles by subsequent calcination. The formation processes of the above 1D borate containing products were investigated and the as-obtained four kinds of borates were studied as novel anode materials. It was found that the MnOBO nanorods displayed the best performance among the four borates, delivering an initial discharge capacitiy of 1,172 mAh·g at 100 mA·g, and 724 mAh·g could be retained after 120 cycles. A full battery composed of a MnOBO nanorod anode and a commercial LiFePO (or LiCoO) cathode has also been assembled for the first time, which delivered an initial discharge capacity of 949 mAh·g (779 mAh·g for LiCoO). The excellent cycle and rate performances of the products reveal their potential applications as anodes for LIBs. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

High-pressure synthesis and crystal structures of the homologous series AuBa2(Ca,Ln)n−1CunO2n+3 (n = 1–4; Ln = rare-earth cations) are described. Their crystal structures and superconducting properties are compared with the corresponding members of the Hg-homologous series. Numerous cuprates containing flat structural fragments (CuO4, CO3 and BO3) synthesized mainly at high pressure are compared in terms of structural peculiarities and superconducting properties. Importance and future prospects of high-pressure application for the preparation of new superconducting oxides are discussed. [ABSTRACT FROM AUTHOR]

In situ Raman spectroscopy and x-ray diffraction measurements are used to explore the structural stability of CaB6 at high pressures and room temperature. The results show no evidence of structural phase transitions up to at least 40 GPa. The obtained equation of state with smooth pressure dependencies yields a zero-pressure isothermal bulk modulus B0 = 170 (5) GPa, which agrees well with the previous measurements. The frequency shifts for A1g, Eg, and T2g vibrational modes of polycrystalline CaB6 are obtained with pressure uploading. As the pressure increases, all the vibration modes have smooth monotonic pressure dependence. The Grüneisen parameter of Eg modes is the largest, indicating its largest dependence on the volume of a crystal lattice. [ABSTRACT FROM AUTHOR]