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Inelastic neutron scattering (INS) was used for determining the crystalline electric field (CEF) energy level scheme of the heavy fermion superconductor CeCoIn5. The orbital fluctuations contributing to superconductivity are affected by the shape of the f orbitals under the influence of the CEF.

Abstract: Temperature dependencies of the nuclear spin-relaxation rate and specific heat of PuCoGa5 and isostructural PuRhGa5 are consistent with their superconductivity being unconventional. A simple model of hybridization between localized f-electrons and itinerant conduction-band electrons gives a framework for interpreting basic similarities and differences between these Pu-based superconductors and their Ce-based analogs. This model also provides a rationale for the correlation between T c and a characteristic spin-energy scale in these materials. [Copyright &y& Elsevier]

Develops an ozone trapping system designed for safe and consistent delivery to a reaction vessel. Use of silica gel to trap the ozone; Significance of using silica gel; Observation of the absence of liquid baths in the trapping system.

Novel zinc-blende (zb) group-IV binary XC and ternary XxY1−xC alloys (X, Y ≡ Si, Ge, and Sn) have recently gained scientific and technological interest as promising alternatives to silicon for high-temperature, high-power optoelectronics, gas sensing and photovoltaic applications. Despite numerous efforts made to simulate the structural, electronic, and dynamical properties of binary materials, no vibrational and/or thermodynamic studies exist for the ternary alloys. By adopting a realistic rigid-ion-model (RIM), we have reported methodical calculations to comprehend the lattice dynamics and thermodynamic traits of both binary and ternary compounds. With appropriate interatomic force constants (IFCs) of XC at ambient pressure, the study of phonon dispersions ω j q → offered positive values of acoustic modes in the entire Brillouin zone (BZ)—implying their structural stability. For XxY1−xC, we have used Green's function (GF) theory in the virtual crystal approximation to calculate composition x, dependent ω j q → and one phonon density of states g ω . With no additional IFCs, the RIM GF approach has provided complete ω j q → in the crystallographic directions for both optical and acoustical phonon branches. In quasi-harmonic approximation, the theory predicted thermodynamic characteristics (e.g., Debye temperature ΘD(T) and specific heat Cv(T)) for XxY1−xC alloys. Unlike SiC, the GeC, SnC and GexSn1−xC materials have exhibited weak IFCs with low [high] values of ΘD(T) [Cv(T)]. We feel that the latter materials may not be suitable as fuel-cladding layers in nuclear reactors and high-temperature applications. However, the XC and XxY1−xC can still be used to design multi-quantum well or superlattice-based micro-/nano devices for different strategic and civilian application needs. [ABSTRACT FROM AUTHOR]

In a previous investigation, the authors proposed nitrogen as a possible candidate for exploiting the donor spin in silicon quantum devices. This system is characterized by a ground state deeper than the other group V impurities in silicon, offering less stringent requirements on the device temperature necessary to access the unionized state. The nitrogen donor is slightly displaced from the substitutional site, and upon heating, the system undergoes a motional transition. In the present article, we show the results from our investigation on the spin–relaxation times in natSi and 28Si substrates and discuss the motional effects on relaxation. The stretched exponential relaxation observed is interpreted as a distribution of spin–lattice relaxation times, whose origin is also discussed. This information greatly contributes to the assessment of a nitrogen-doped silicon system as a potential candidate for quantum devices working at temperatures higher than those required for other group V donors in silicon. [ABSTRACT FROM AUTHOR]

Abstract: We report 235U and 121Sb NMR in the antiferromagnetic state of . Our spectra agree with previous reports by Kato et al., however, we find evidence to suggest three distinct magnetic environments. The temperature dependence of the Sb spin lattice relaxation rate reveals a crossover to Korringa-like metallic behavior below 7K. We interpret this behavior as arising from conduction electrons scattering below the magnon excitation gap. [Copyright &y& Elsevier]

The field of mathematics that studies the relationship between algebraic structures and graphs is known as algebraic graph theory. It incorporates concepts from graph theory, which examines the characteristics and topology of graphs, with those from abstract algebra, which deals with algebraic structures such as groups, rings, and fields. If the vertex set of a graph G ^ is fully made up of the zero divisors of the modular ring Z n , the graph is said to be a zero-divisor graph. If the products of two vertices are equal to zero under (modn), they are regarded as neighbors. Entropy, a notion taken from information theory and used in graph theory, measures the degree of uncertainty or unpredictability associated with a graph or its constituent elements. Entropy measurements may be used to calculate the structural complexity and information complexity of graphs. The first, second and second modified Zagrebs, general and inverse general Randics, third and fifth symmetric divisions, harmonic and inverse sum indices, and forgotten topological indices are a few topological indices that are examined in this article for particular families of zero-divisor graphs. A numerical and graphical comparison of computed topological indices over a proposed structure has been studied. Furthermore, different kinds of entropies, such as the first, second, and third redefined Zagreb, are also investigated for a number of families of zero-divisor graphs. [ABSTRACT FROM AUTHOR]

The Au–B–C and Cu–B–C growth systems, which do not form borides, have been used for the first time for the synthesis of boron-doped superconducting diamond. In these systems, the graphite-to-diamond transformation occurs at pressures from 8 to 9 GPa and temperatures from 1620 to 1770 K, suitable for commercial-scale production. The presence of boron in melts is assumed to be responsible for the decrease in synthesis temperature in molten copper and the diamond-forming ability of gold-based melts. The synthesized diamond exhibits metallic behavior of conductivity at ordinary temperatures and undergoes a superconducting transition between 4.5 and 2.5 K. [ABSTRACT FROM AUTHOR]

To describe non-Debye relaxation phenomena observed in dielectric materials, the Cole–Cole (CC) relaxation model in the frequency domain and the Kohlrausch–Williams–Watts (KWW) relaxation model in the time domain were introduced in the physics of dielectrics. In this paper, we propose a new relaxation model with two parameters besides a relaxation time by expressing the relaxation function in the time domain in terms of the Mittag–Leffler functions. The proposed model represents a group of non-Debye relaxation phenomena and shows a transition between the CC and the KWW models. The relaxation properties described by the new model are analyzed, including the response function, the normalized complex dielectric permittivity, dielectric storage and loss factors as well as the relaxation frequency and time spectral functions. The presented relaxation function has a concise form and is expected to be applied to more complex relaxation phenomena. [ABSTRACT FROM AUTHOR]

The mechanisms of physical processes at the metal/La1–xSrxMnO3 manganite interfaces that determine the memristive properties of structures based on them were investigated experimentally and by numerical modeling. The transport properties of percolation channels of memristive structures based on epitaxial La1–xSrxMnO3–δ films were studied. It is shown that resistive switching in the studied structures is controlled by two processes. These are a change in the resistive state of the normal metal–oxide interface under the action of alternating voltage and electro diffusion of oxygen to vacancies, while the level of doping (oxygen) of the conducting channel changes, the electric field potential is redistributed, as a result, the resistive properties of the heterocontact change. The calculations showed that each successive transition of the heterostructure from the OFF to the ON state significantly depends not only on the switching voltage but also on the size and location of the gap structure that has been preserved from the previous switching from ON to OFF. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) is a powerful local quantum probe of the electronic structure of materials, but in the absence of reliable theory the interpretation of the NMR data can be challenging. This is true in particular for the cuprate high-temperature superconductors. Over the years, a large base of NMR data became available, which makes a review of early assumptions possible. Very recently, it was shown that all planar 17 O NMR shift and relaxation data available in the literature point to a temperature-independent but doping-dependent pseudogap, very similar to what was proposed from the electronic entropy. Here we analyze shift and relaxation of planar O to see whether it follows the very anisotropic and temperature-dependent Cu shift scenario. We find that the O data show a simple, temperature-independent anisotropy in agreement with hyperfine coefficients and orbital shifts predicted by first principles. Furthermore, we show that the original 89 Y shift and relaxation data are in agreement with the proposed temperature-independent pseudogap. This pseudogap depends on doping, but also on the family of materials, and the density of states outside or in the absence of the gap is universal for the cuprates; this suggests that the entropy should be similar for all cuprates, as well. Further consequences will be discussed. [ABSTRACT FROM AUTHOR]

Black diamond is an emerging material for solar applications. The femtosecond laser surface treatment of pristine transparent diamond allows the solar absorptance to be increased to values greater than 90% from semi-transparency conditions. In addition, the defects introduced by fs-laser treatment strongly increase the diamond surface electrical conductivity and a very-low activation energy is observed at room temperature. In this work, the investigation of electronic transport mechanisms of a fs-laser nanotextured diamond surface is reported. The charge transport was studied down to cryogenic temperatures, in the 30–300 K range. The samples show an activation energy of a few tens of meV in the highest temperature interval and for T < 50 K, the activation energy diminishes to a few meV. Moreover, thanks to fast cycles of measurement, we noticed that the black-diamond samples also seem to show a behavior close to ferromagnetic materials, suggesting electron spin influence over the transport properties. The mentioned properties open a new perspective in designing novel diamond-based biosensors and a deep knowledge of the charge-carrier transport in black diamond becomes fundamental. [ABSTRACT FROM AUTHOR]

A phonon of appropriate momentum k F will open a band gap at the Fermi energy E F . The gap within the electronic density-of-states (DOS), N (E F) , leads to a gain in electronic energy and a loss of elastic energy because of the gap-generating phonon. A BCS-like simulation shows that the energy gain is larger than the loss for temperatures below a certain transition temperature, T C . Here, it is shown that the energy count can be almost as favorable for gaps a little below or above E F . Such gaps can be generated by auxiliary phonons (or even spin- and charge-density waves) with k-vectors slightly different from k F . Gaps not too far from E F will add to the energy gain at the superconducting transition. In addition, a DOS-peak can appear at E F and thereby increase N (E F) and T C . A dip in the DOS below E F will result for temperatures below T C , which is similar to what often is observed in cuprate superconductors. The roles of spin waves and thermal disorders are discussed. [ABSTRACT FROM AUTHOR]

Recently, an analysis of all available planar oxygen shift and relaxation data for the cuprate high-temperature superconductors showed that the data can be understood with a simple spin susceptibility from a metallic density of states common to all cuprates. It carries a doping dependent but temperature independent pseudogap at the Fermi surface, which causes the deviations from normal metallic behavior, also in the specific heat. Here, a more coherent, unbiased assessment of all data, including planar Cu, is presented and consequences are discussed, since the planar Cu data were collected and analyzed prior to the O data. The main finding is that the planar Cu shifts for one direction of the external magnetic field largely follow from the same states and pseudogap. This explains the shift suppression stated more recently, which leads to the failure of the Korringa relation in contrast to an enhancement of the relaxation due to antiferromagnetic spin fluctuations originally proposed. However, there is still the need for a second spin component that appears to be associated with the Cu 3 d (x 2 − y 2) hole to explain the complex Cu shift anisotropy and family dependence. Furthermore, it is argued that the planar Cu relaxation which was reported recently to be rather ubiquitous for the cuprates, must be related to this universal density of states and the second spin component, while not being affected by the simple pseudogap. Thus, while this universal metallic density of states with a pseudogap is also found in the planar Cu data, there is still need for a more elaborate scenario that eludes planar O. [ABSTRACT FROM AUTHOR]

In this work, we study crystalline electric field effects in the heavy fermion superconductor CeIrIn 5 . We observe two regions of broad magnetic response in the inelastic neutron scattering (INS) spectra at 10 K. The first corresponds to the transition between the Γ 7 groundstate doublet and the first excited state doublet at 4 meV interwoven with a broad quasielastic contribution. The second region corresponds to the transition between the ground state and the second excited state doublet at 28 meV. The large Lorentzian half-widths of the peaks (&nvsim;10 meV) calls into question calculations for the specific heat and magnetic susceptibility that assume sharp crystal field (CF) levels. Consequently, we have calculated the INS spectra and magnetic susceptibility using the Anderson impurity model within the non-crossing approximation including the effects of CF level splitting. [ABSTRACT FROM AUTHOR]

Abstract: We present an In(1) NQR study on the heavy-fermion (HF) compound CeCo(In1−x Cd x )5 . Bulk measurements indicate that Cd doping acts as an electronic tuning agent in CeCoIn5, and that superconductivity (SC) and antiferromagnetism (AFM) may coexist at ambient pressure for . For , the nuclear spin lattice relaxation rate shows a broad peak at the Néel temperature , with a subsequent onset of SC at . Our results provide strong evidence for microscopic coexistence of these two ground states. The nuclear magnetization recovery curves in both the ordered and mixed states reveal a single -component, which suggests a homogeneous nature of the Ce-4f1 electronic state. [Copyright &y& Elsevier]

An amorphous carbon (a-C) powder obtained by decomposition of sucrose was mixed with sulfur and synthesized at 400 C. Magnetic measurements reveal that the products obtained are inhomogeneous. Some parts show traces of superconductivity at T=17 and 42 K. Other parts show unusual magnetic features. (i) Pronounced irreversible peaks around 50 K appear in the first zero-field-cooled (ZFC) sweep only. (ii) Unexpectedly, these peaks are totally suppressed in the second ZFC runs performed a few minutes later. Around the peak position, the field-cooled (FC) curves cross the ZFC plots, such that ZFC>FC. The two peculiar magnetic observations are connected to each other and are also ascribed to the a-C powder taken from commercial sources. The possibility that impurities cause these magnetic phenomena is excluded. [ABSTRACT FROM AUTHOR]

We report NQR data on the heavy-fermion compound CeLaCoIn. The NQR spectrum of the In(1) site is composed of five different peaks, which are described by a binomial distribution of the nearest-neighbor La atoms. Our results suggest that an analysis of the NQR spectra yields a more accurate doping level than energy dispersive X-ray spectroscopy (EDS) results. [ABSTRACT FROM AUTHOR]

The presence of boron in the structure of diamond is rare in nature, and even when present, reported values are ≤ 0.5 ppm. This study used various spectroscopic methods and time-of-fight (ToF-) SIMS to characterize and analyze for boron in natural type IIb blue diamonds, including the well-known Hope and the Blue Heart diamonds, and on one high- pressure, high-temperature annealed natural stone. Infrared spectroscopy measurements reveal uncompensated boron values as large as 1.72 ± 0.15 ppm, which is significantly higher than the previously reported maximum of 0.5 ppm. ToF-SIMS analyses gave spot total boron concentrations as high as 8.4 ± 1.1 ppm for the Hope diamond to less than 0.08 ppm in other blue diamonds. By comparison, a type Ia diamond did not show detectable boron. ToF-SIMS analyses revealed strong zoning of boron in some diamonds, which was confirmed by mapping the uncompensated boron using synchrotron infrared spectroscopy. This greater range of boron concentrations compared to previous studies might be explained by the larger number of natural diamonds analyzed here, 78, compared to <10 samples reported in the literature. The samples in this study are all gem-quality diamonds, including some Intense to Fancy-Deep blue diamonds; color intensity, however, only loosely correlates with the boron content. Boron is also likely responsible for the phosphorescence emissions of type IIb diamonds, in the red at 660 nm and in the blue- green at 500 nm. Our results are consistent with previous work suggesting that the emissions are caused by donor-acceptor pair recombination processes involving boron and other defects. The exact nature of the phosphorescence processes is still not fully understood, but likely involves complex steps of charge carrier trapping and detrapping. [ABSTRACT FROM AUTHOR]