scispace - formally typeset
Search or ask a question

Showing papers in "Philosophical Magazine Part B in 2002"


Journal ArticleDOI
TL;DR: Using high-resolution angle-resolved photoemission data in conjunction with that from neutron and other probes, this paper showed that electron-phonon coupling is strong in cuprate superconductors and that phonons play an important role in pairing.
Abstract: Using high-resolution angle-resolved photoemission data in conjunction with that from neutron and other probes, we show that electron-phonon coupling is strong in cuprate superconductors and that it plays an important role in pairing. In addition to the strong electron correlation, the inclusion of phonons provides a theoretical framework explaining many important phenomena that cannot be understood by a strongly correlated electronic model alone. In particular, it is indispensable to explain the difference among materials. The phonons with the wavenumber around the (0, qy ) and (qx , 0) axes create d-wave pairing while that near (π, π) are pair breaking. Therefore the half-breathing mode of the oxygen motions helps d-wave superconductivity.

66 citations


Journal ArticleDOI
TL;DR: In this article, the influence of high dc currents on the interaction between thin Au-Al layers was investigated over the temperature range 400-500°C, in both the absence and the presence of a current at all levels.
Abstract: The influence of high dc currents (up to 1019 A cm−2) on the interaction between thin Au-Al layers was investigated over the temperature range 400-500°C In contrast with earlier diffusion couple results, only four of the five intermetalllic compounds in this system were observed, in both the absence and the presence of a current at all levels The intermetallics Au5 Al2 and Au2 Al were the dominant products while AuAl and AuAl2 were relatively insignificant The latter showed little change, growing only to a total thickness of a few micrometres, regardless of the magnitude of the current density and time of annealing While the sequence of formation of the different intermetallics was not affected by the current, the incubation time and rate of growth of the layers were strongly influenced The incubation time for the appearance of a measurable product layer was markedly reduced by the current, by nearly two orders of magnitude in some cases The effect of the current on the nucleation of the pr

59 citations


Journal ArticleDOI
TL;DR: In this paper, the Fowler-Nordheim (F-N) equation is used to estimate the work function, the enhancement factor, the tip radius and the effective emitting area of an electron field emitters.
Abstract: Some properties of electron field emitters based on various types of carbon are difficult to measure and are not well known. This is particularly true for amorphous carbon films, for nanotubes and for nanotips grown by carbon contamination in a scanning electron microscope. We show that by combining together experimental data (i.e. emitter geometry from electron microscopy observations, and field emission current and applied voltage measurements), numerically computed values of the electric field at the tip surface and the Fowler-Nordheim (F-N) equation, it is possible to estimate values of parameters such as the work function, the enhancement factor, the tip radius and the effective emitting area. The general applicability of this approach and corresponding results are emphasized. We also show that, when the experimental parameters that are known are superfluous in number (i.e. more than the minimum number needed), a discrepancy exists, firstly, between the value of the emitter radius worked out...

46 citations


Journal ArticleDOI
TL;DR: In this article, the local segmental α relaxation in 15-20 nm poly(methyl phenyl siloxane) (PMPS) films was shown to be much faster and had a significantly weaker temperature dependence compared to the bulk polymer.
Abstract: Two recent experiments have shown dramatic changes in molecular dynamics when the size of the glass formers is reduced to the nanometre scale but in opposite directions The first is a dielectric relaxation study by Anastasiadis et al of the local segmental α relaxation in 15-20 nm poly(methyl phenyl siloxane) (PMPS) films confined between parallel solid surfaces of silicate nanocomposites The α relaxation was observed to be much faster and had a significantly weaker temperature dependence compared to the bulk polymer The other experiment is a molecular dynamics computer simulation by Scheidler et al of a binary Lennard-Jones liquid confined either in a cylindrical pore or as a thin film confined between two walls In the simulation, the walls were made of an amorphous structure similar to that of the confined liquid but the particles in the walls were fixed in position The mobile particles inside the pore or in the thin film interact with each other and with the wall particles by the same

42 citations


Journal ArticleDOI
TL;DR: In this article, the effect of the difference between the refractive indices of the glass particles and the epoxy matrix on the light transmittance of the composite is obtained, which is correlated with the relationship between the wavelength dispersion curves.
Abstract: Glass particles with a size d p of 38–53 μm are incorporated into a clear epoxy matrix and the light transmittance T L of the composites is measured in the wavelength γ range from 200 to 1100 nm. The net difference ▵n c between the refractive indices of the glass particles and the matrix of the fabricated composite ranged from nearly zero to 0.03. This difference between the refractive indices is achieved by, firstly, selecting the optical properties of dispersed glass particles and secondly, changing the thermal stress in the composite. The effect of the difference ▵n c between the refractive indices of the glass particles and the epoxy matrix on the light transmittance of the composite is obtained. It is found that the light transmission spectrum of the composite is correlated with the relationship between the wavelength dispersion curves of the refractive indices of the glass particles and the matrix. At a fixed wavelength, the T L−▵n c curve is only dependent on the particle size and volume f...

39 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present the results of molecular dynamics computer simulations of a simple glass former close to an interface between the liquid and the frozen amorphous phase of the same material, and show that the relaxation dynamics of the particles close to the wall are much slower than those for particles far away from the wall.
Abstract: We present the results of molecular dynamics computer simulations of a simple glass former close to an interface between the liquid and the frozen amorphous phase of the same material. By investigating F s (q, z, t), the incoherent intermediate scattering function for particles that have a distance z from the wall, we show that the relaxation dynamics of the particles close to the wall are much slower than those for particles far away from the wall. For small z the typical relaxation time for Fs (q, z, t) increases as exp [Δ/(z - z p)], where Δ and z p are constants. We use the location of the crossover from this law to the bulk behaviour to define a first length scale [ztilde]. A different length scale is defined by considering the Ansatz F s(q, z, t) = F s bulk(q, t) + a(t) exp {-[z/ξ(t)]β(1)}, where a(t), ξ(t) and β(t) are fit parameters. We show that this Ansatz gives a very good description of the data for all times and all values of z. The length ξ(t) increases for short and intermediate ti...

34 citations


Journal ArticleDOI
TL;DR: In this paper, the anomalous thermal expansion behavior of Pu-Ga alloys can be explained by an Invar effect, which is modelled by assuming the thermal transfer of Pu atoms from a lower-energy higher-volume Δ1, state to a higher-energy lower volume Δ2 state.
Abstract: We show that the anomalous thermal expansion behaviour of Pu-Ga alloys can be explained by an Invar effect, which is modelled by assuming the thermal transfer of Pu atoms from a lower-energy higher-volume Δ1, state to a higher-energy lower-volume Δ2 state. The energy separation of these states is found to be 1400 K from a fit to the available neutron diffraction data on the lattice constants of Pu-Ga alloys. The Invar model enables a precise evaluation of the coefficient of thermal expansion and of the Gruneisen constant. The addition of Ga forces a stabilization of the Δ2 state and suppresses the negative thermal expansion.

29 citations


Journal ArticleDOI
TL;DR: In this paper, an analysis of the electronic properties of bulk cubic and hexagonal diamond calculated using the ab initio packages CRYSTAL98 and the Vienna Ab initio Simulation Package is presented.
Abstract: An analysis of the electronic properties of bulk cubic and hexagonal diamond calculated using the ab initio packages CRYSTAL98 and the Vienna Ab initio Simulation Package is presented. We apply these ab initio methods to the study of cubic diamond, including the calculation of electronic properties (such as the band structure, electronic density of states, the indirect bandgap E indirect g, the valence band width and the conduction band width) and mechanical properties (such as the equilibrium lattice constant a 0 and the bulk modulus B). The combination of theoretical techniques that yield results that most accurately match experiment for cubic diamond are then used to calculate the electronic properties of the hexagonal diamond polymorph.

29 citations


Journal ArticleDOI
TL;DR: In this paper, the authors report results of controlled devitrification of rare-earth-doped glasses made in order to improve the initial spectroscopic properties of the as-melted glass to obtain crystal-like properties.
Abstract: We report results of controlled devitrification of rare-earth-doped glasses made in order to improve the initial spectroscopic properties of the as-melted glass to obtain crystal-like properties. This study is made to allow the design of reduced-size photonic devices owing to the use of more efficient active materials. The main possibilities of devitrification of glasses are evaluated in two glassy systems and compared. The key point is the choice of the glass composition allowing partial crystallization during thermal treatments adapted to the thermal stability of the material. A strong improvement in the spectroscopic properties of the rare-earth ions has been obtained in a heterogeneously nucleated glass (GeO2–PbO–PbF2). The final glass-ceramic is ultratransparent with weak additional losses mainly in the short-wavelength region. Another possibility has been evaluated through the spinodal decomposition of a fluorozirconate glass (ZrF4–LaF3–AlF3–GaF3–ErF3). Its spectroscopic properties are also...

28 citations


Journal ArticleDOI
TL;DR: In this article, rare earth-doped (Er−, Yb− and Er+ Ybdoped) silica glasses have been produced and characterized and their spectroscopic properties have been assessed.
Abstract: Rare-earth-doped (Er−, Yb− and Er+ Yb-doped) silica glasses have been produced and characterized. Their spectroscopic properties have been assessed and optical amplification devices have been produced therefrom and characterized.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the Coulomb couplings in the highest occupied orbital of molecular C60 were computed based on density-functional electronic-structure calculations, and they were obtained a multiplet-averaged Hubbard U ≈ 3 eV, and four Hund-rule-like intramolecular multiplet splitting terms.
Abstract: We compute, based on density-functional electronic-structure calculations, the Coulomb couplings in the hu highest occupied orbital of molecular C60. We obtain a multiplet-averaged Hubbard U ≈ 3 eV, and four Hund-rule-like intramolecular multiplet-splitting terms, each of the order of a few hundred millielectronvolts. According to these couplings, all Cn+ 60 ions should possess a high-spin ground state if kept in their rigid undistorted form. Even after molecular distortions are allowed, however, the Coulomb terms still appear to be somewhat stronger than the previously calculated Jahn–Teller couplings, the latter favouring low-spin states. Thus for example in C2+ 60, unlike C2- 60, the balance between the Hund rule and Jahn–Teller yields, even if marginally, a high-spin ground state. That seems surprising in view of reports of superconductivity in field-doped Cn+ 60 systems.

Journal ArticleDOI
TL;DR: In this article, the authors present some results on MNCG films prepared by ion implantation and demonstrate the presence of thermal nonlinearity in the optical response for rf sputtered films.
Abstract: Metal nanocluster composite glasses (MNCGs) have been the subject of both experimental and theoretical investigation because of their peculiar optical properties. In particular, the enhanced third-order optical nonlinearity could be exploited in the all-optical switching device technology. Nevertheless, several factors such as thermal stability, wavelength tunability, response time regime, recycling frequency, laser-induced damage and optical absorption come into play in the definition of the material suitability. In this work, we present some results on MNCG films prepared by ion implantation. Nonlinear refractive index values are also presented for rf sputtered films, evidencing the presence of thermal nonlinearity in the optical response. Figures of merit that must be satisfied for ultrafast all-optical switching application of MNCGs are evaluated for this composite.

Journal ArticleDOI
TL;DR: In this article, a pump-probe configuration was used to detect nonlinear optical effects in a bis-sodium bis-diethylsulphosuccinate-decane microemulsion near the percolation line and far from critical points.
Abstract: Nonlinear optical effects in a water-sodium bis-diethylsulphosuccinate-decane microemulsion near the percolation line and far from critical points are reported and experimentally studied. We use a pump-probe configuration: a probe red Gaussian beam from a He-Ne laser is focused by a converging lens. The Gaussian-shaped TEM00 mode of an Ar+ laser is focused behind a thin film of microemulsion that is located behind the focal plane of the probe. Observation of the temporal behaviour of the detected signal allows one to distinguish a fast negative nonlinear optical effect, attributed to thermal blooming by a slow positive nonlinear optical effect attributed to mass diffusion due to the Soret effect and electrostriction. Maximum nonlinearity is observed for parallel polarizations of the pump and probe beams. Turning off the pump beam, the thermal profile and consequent nonlinear effect disappear. The existence of the concentration profile and of the consequent converging lens effect is clearly detect...

Journal ArticleDOI
TL;DR: In this article, a mechanism based on direct exchange coupling between the tunnelling electrons and the local precessing spin S was proposed to detect the precession of a single spin.
Abstract: Electron spin resonance-scanning tunnelling microscopy is an emerging technique which is capable of detecting the precession of a single spin. We discuss a mechanism based on direct exchange coupling between the tunnelling electrons and the local precessing spin S. We claim that, since the number of tunnelling electrons in a single precessing period is small (about 20), one may expect a net temporary polarization within this period which will couple via exchange interaction to the localized spin. This coupling will modulate the tunnelling barrier with the Larmor frequency of the precessing spin ωL. This modulation, although randomly changing from cycle to cycle, will produce an elevated noise in the current at ωL. We find that for relevant values of parameters the signal-to-noise ratio in the spectral characteristic is 2–4 and is comparable with the values of the signal-to-noise ratio reported by Manassen and co-workers and by Durkan and Welland. The magnitude of the current fluctuation is a rela...

Journal ArticleDOI
TL;DR: In this paper, the geometry and electronic structure of an interstitial H atom in the BaTiO3 crystal considering both cubic and tetragonal crystallographic lattices were investigated. And the role of the H impurity in ferroelectric polarization was analyzed.
Abstract: We investigate the geometry and electronic structure of an interstitial H atom in the BaTiO3 crystal considering both cubic and tetragonal crystallographic lattices. A quantum-chemical method based on the Hartree-Fock formalism is used throughout the study. Interstitial H is found to bind to one of the O atoms, forming the so-called OH group. At equilibrium, the O-H distances are found to be 0.89 and 0.91 A for cubic and tetragonal lattices respectively. The performed automated geometry optimization procedure of the defective region shows considerable outward movements of atoms closest to the impurity. The role of the H impurity in ferroelectric polarization in the BaTiO3 crystal is analysed using the results obtained in connection with the available experimental data on ferroelectric perovskites.

Journal ArticleDOI
TL;DR: In this paper, the molecular structure of GexS100-x glasses in the 30 < x < 34 atomic percentage range is examined by Raman scattering, 119Sn Mossbauer spectroscopy, and temperature-modulated differential scanning calorimetry.
Abstract: Molecular structure of GexS100-x glasses in the 30 < x < 34 atomic percentage range is examined by Raman scattering, 119Sn Mossbauer spectroscopy, and temperature-modulated differential scanning calorimetry. The results show that the stoichiometric glass with x = 33.33 (T g = 508°C) is chemically disordered. Raman scattering places mode strengths of corner-sharing Ge(S1/2)4 tetrahedra (A), ethane-like Ge2(S1/2)6 units (B), and the distorted rocksalt Ge(S1/6)6 units (C) at approximately 93.4:3.6:3.0 not normalized for mode cross-sections. Mossbauer spectroscopy places the concentration of these units as A : B : C = 76.2:8.8 :15. The drastic reduction in the slope of the glass transition temperature T g with Ge content x coincides with first appearance of these units once x exceeds 32.50, suggesting that these units are demixed and form separate nanophases to lower the global connectivity of the glass network.

Journal ArticleDOI
TL;DR: In this paper, the existence of five compounds with the chemical formulae U5Ge4, UGe5, U3Ge5 and UGe2 has been investigated.
Abstract: The recent more thorough reinvestigation of the U–Ge system has finally established the existence of five compounds with the chemical formulae U5Ge4, UGe, U3Ge5, UGe2 and UGe3. Here we add another compound UGe2-x, existing in a homogeneity range of 0.30 0.35, and crystallizing in the defect tetragonal ThSi2-type structure. This compound is a ferromagnet with T c = 47 K. For all these compounds we have revised earlier measured magnetic properties and measured (often for the first time) the magnetotransport properties such as the electrical resistivity at 0T and in applied magnetic fields up to 8 T. We have found no superconducting properties for U5Ge4 down to 20 mK, which was claimed earlier. The most striking features found for both ferromagnets UGe2-x (ThSi2-type phase) and UGe2 (ZrGa2-type phase) are their temperature dependences of the magnetoresistivity (MR). At low temperatures the MRs for both these phases are large and positive which, above 10 and 15 K respectively, change sign to ne...

Journal ArticleDOI
TL;DR: Amorphous tris(8-hydroxyquinoline) aluminium (Alq3) thin films were deposited on fused silica substrates by thermal evaporation and optical absorption, emission and excitation spectra were measured at room temperature and, for the first time, at 80 K, on an Alq3 film in a spectral range extending from the near ultraviolet to the visible.
Abstract: Amorphous tris(8-hydroxyquinoline) aluminium (Alq3) thin films were deposited on fused silica substrates by thermal evaporation. Optical absorption, emission and excitation spectra were measured at room temperature and, for the first time, at 80 K, on an Alq3 film in a spectral range extending from the near ultraviolet to the visible. Spectroscopic features were carefully investigated as a function of temperature.

Journal ArticleDOI
TL;DR: In this article, the authors measured the dynamics of the fragile glass former m-toluidine in its supercooled phase by the time-resolved optical Kerr effect.
Abstract: We measured the dynamics of the fragile glass former m-toluidine in its supercooled phase by the time-resolved optical Kerr effect. Using an experimental time filtering of the internal molecular vibrations a better insight into the fast relaxation processes has been achieved. We analysed the dynamic features of these fast processes and compared them with the mode-coupling theory predictions.

Journal ArticleDOI
TL;DR: In this article, structural and optical properties and defects of a-Si1-x C x :H films grown by plasma-enhanced chemical vapour deposition in a silane-methane plasma at rf power densities up to 60mW cm−2 and with carbon contents x up to 0.6.
Abstract: Hydrogenated amorphous silicon-carbon alloys (a-Si1-x C x :H) deposited by plasma techniques are important for a large variety of applications from microelectronics and optoelectronics to microelectromechanic and photonic structures. However, it is known that as the carbon concentration increases in the alloy, the properties of the films strongly depend on the deposition technique and growth conditions. The aim of the present work is the investigation of structural and optical properties and defects of a-Si1-x C x :H films grown by plasma-enhanced chemical vapour deposition in a silane-methane plasma at rf power densities up to 60mW cm−2 and with carbon contents x up to 0.6. Films have been produced and characterized with low defect densities, below 1.3 × 1017cm−3, deposition rates higher than 0.1 nm s−1, evidence of chemical order for a near-stoichiometric region and high radiative efficiency. The results have been discussed in the light of Consolidated models of the deposition chemistry, struct...

Journal ArticleDOI
TL;DR: In this article, the Wooten-Winer-Weaire bond-switching algorithm was used to generate low-strain amorphous and paracrystalline networks of up to 10000 atoms.
Abstract: We report on recent progress in the development of new techniques to generate high-quality models of continuous random networks, which are used as models for elemental and binary tetrahedral semiconductors such as amorphous Si and amorphous GaAs. The availability of such models has allowed us to look at a number of outstanding issues regarding their electronic properties, the fundamental role of defects and dynamics. We describe briefly our modifications made to the Wooten-Winer-Weaire bond-switching algorithm, allowing us to produce low-strain amorphous and paracrystalline networks of up to 10000 atoms. Then some of the structural and electronic properties of these models are presented. We also discuss briefly some recent results on the recrystallization of amorphous networks.

Journal ArticleDOI
TL;DR: An efficient collision detection scheme for spherical grains of various sizes based on a dynamic three-dimensional Delaunay triangulation is presented and the remaining requirements for a complete DEM simulation are addressed.
Abstract: The distinct element method (DEM) is an approach to modelling and simulation well suited to the study of discontinuous phenomena By tracking each element individually and dealing explicitly with every interaction among the elements, the DEM allows one to deduce statistical behaviour of the assembly Realistic simulation of granular materials has largely benefited from this relatively recent approach In particular, it is now possible to address specific phenomena such as arching effects, flows and packings in three dimensions and to make them observable, which is impossible or at least extremely complicated to achieve with physical experiments Two major issues arise in the context of DEM: efficient detection of the interactions between the grains and numerical modelling of the physical contacts This paper focuses on the former by presenting an efficient collision detection scheme for spherical grains of various sizes based on a dynamic three- dimensional Delaunay triangulation Aside from the theoretical and practical discussion of this scheme, the remaining requirements for a complete DEM simulation are also addressed Finally, examples are given to illustrate the potential of this approach

Journal ArticleDOI
TL;DR: In a pure silica glass, different fictive temperatures are achieved between 1500 and 1100°C as discussed by the authors, and the position of the Si-O-Si Raman band is checked by the position.
Abstract: In a pure silica glass, different fictive temperatures are achieved between 1500 and 1100°C. These temperatures are checked by the position of the Si–O–Si Raman band. Light scattering for the different samples due to density fluctuations is determined by the Landau-Placzek ratio which decreases when T f decreases. Further relaxation occurs in this glass 300°C below T g; it is interpreted in correlation with the subrelaxational process induced by the diffusion of a few parts per million of impurities.

Journal ArticleDOI
TL;DR: In this article, the energy eigenvalues of excitonic states in amorphous semiconductors were derived by applying the effective mass approach, and it was shown that Wannier-Mott-type excitons can indeed be formed in ammorphous solids.
Abstract: Applying the effective-mass approach, the energy eigenvalues of excitonic states in amorphous semiconductors are derived. It is shown that Wannier–Mott-type excitons can indeed be formed in amorphous solids. The results show that the occurrence of the double photoluminescence (PL) lifetime distribution peak, fast and slow, in hydrogenated amorphous silicon (a-Si: H) and hydrogenated amorphous germanium (a-Ge: H) can unambiguously be assigned to radiative recombinations from singlet and triplet excitonic states respectively. The dependence of PL peaks on the temperature and generation rate in a-Si: H and a-Ge: H is also discussed. The approach is general and simple and can be applied to study the charge-carrier transport and PL properties in any amorphous solid.

Journal ArticleDOI
TL;DR: In this paper, a new analysis of electronic transport in chalcogenide glasses, based on bipolaron hopping in the extended pair approximation, is presented, where the relaxation time of the carrier when hopping has a Meyer-Neldel type of temperature dependence instead of a simple activated form.
Abstract: A new analysis of electronic transport in chalcogenide glasses, based on bipolaron hopping in the extended pair approximation, is presented. It is assumed that the relaxation time of the carrier when hopping has a Meyer-Neldel type of temperature dependence instead of a simple activated form. In this way, the experimental data for both dc conductivity and ac conductivity can be fitted over a wide range of temperatures, and for a number of glasses using the same set of parameters.

Journal ArticleDOI
TL;DR: In this paper, the authors explicitly calculate the four leading-order terms of the formal asymptotic series for large |∊| (where ∊ denotes the external energy parameter) of the single-particle Green function G σ(∊), σ e {−s, −s + 1, …, s}, and the three leading order terms of that of the self-energy operator ∑σ( ∊), pertaining to systems of spin-s fermions (s is a half-integer) in d-dimensional spatial space, interacting through
Abstract: We explicitly calculate the four leading-order terms of the formal asymptotic series for large |∊| (where ∊ denotes the external energy parameter) of the single-particle Green function G σ(∊), σ e {−s, −s + 1, …, s}, and the three leading-order terms of that of the self-energy operator ∑σ(∊), pertaining to systems of spin-s fermions (s is a half-integer) in d-dimensional spatial space, interacting through an arbitrary two-body potential v(r-r'). These contributions, which are expressed in terms at most of a three-body static ground-state correlation function, are amenable to accurate numerical calculation through employing correlated many-particle ground-state wavefunctions such as determined within, for example, the quantum Monte Carlo framework. Such calculations will provide indisputably reliable information with regard to the spectral function of the single-particle excitations at high energies of correlated systems, as well as energy moments of this spectral function, and thus help to assess...

Journal ArticleDOI
TL;DR: In this article, a new Adam-Gibbs model was proposed to describe the structural relaxation time in glass-forming systems, where the configurational entropy has been written in terms of the excess heat capacity and the molar thermal expansion.
Abstract: The pressure and temperature behaviours of the structural relaxation time in glass-forming systems can be well described by a new equation, based on the Adam-Gibbs model, where the configurational entropy has been written in terms of the excess heat capacity and the molar thermal expansion. An experimental check of this equation was performed on the dynamics of an epoxy compound, investigated by wide-band dielectric spectroscopy (10−2–1010Hz). Six different sets of relaxation data, corresponding to two different conditions, were analysed: firstly, isobaric (atmospheric pressure and 95.5 MPa) with various temperatures down to the supercooled and glassy phases and, secondly, isothermal (at four different temperatures) with changing pressure in the range 0.1–270 MPa. Moreover, the thermal expansion was independently determined from data on the pressure and temperature variations of the volume of the material. From this analysis, the pressure-extended Adam-Gibbs model resulted, which is so suitable f...

Journal ArticleDOI
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) and Xray and neutron diffraction measurements were carried out on the compound CeRhSn, and the results showed that electrical resistivity ρ, magnetic susceptibility χ, specific heat C, and XPS were all present.
Abstract: Electrical resistivity ρ, magnetic susceptibility χ, specific heat C, X-ray photoelectron spectroscopy (XPS) and X-ray and neutron diffraction measurements were made on the compound CeRhSn. The mea...

Journal ArticleDOI
TL;DR: In this article, the Meissner-Ochsenfeld state, screening supercurrents and hysteresis loops of type II superconductors were observed from the temperature and magnetic field dependences of the magnetic moment m(T,H) in graphite powders reacted with sulphur for temperatures below 9.0K.
Abstract: Superconducting characteristics such as the Meissner–Ochsenfeld state, screening supercurrents and hysteresis loops of type II superconductors were observed from the temperature and magnetic field dependences of the magnetic moment m(T,H) in graphite powders reacted with sulphur for temperatures below 9.0K. The temperature dependence of the lower critical field H cl (T) was determined and the zero-temperature penetration depth λ(0) was estimated (λ(0) = 2270 A). The superconductivity was observed to be highly anisotropic and to coexist with a ferromagnetic state that has a Curie temperature well above room temperature. A continuous transition from the superconducting state to the ferromagnetic state could be achieved by simply increasing the applied magnetic field.

Journal ArticleDOI
TL;DR: In this article, the de Haas-van Alphen (dHvA) experiment was carried out on a high-quality single-crystal CeAgSb2, which has a small net ferromagnetic moment of 0.4 μB per Ce atom.
Abstract: We have carried out the de Haas-van Alphen (dHvA) experiment, together with electrical resistivity, magnetic susceptibility, magnetization and specific heat experiments on a high-quality single-crystal CeAgSb2, which has a small net ferromagnetic moment of 0.4 μB per Ce atom. The bulk magnetic properties are well explained by the crystalline electric field scheme. On the other hand, large dHvA frequencies of 108 Oe, which correspond to cylindrical Fermi surfaces, were detected by the dHvA measurement for the magnetic field along the tetragonal [001] direction, indicating the quasi-two-dimensional electronic structure. The dHvA branches of CeAgSb2 are highly different from those with small dHvA frequencies of 107 Oe for the reference compounds LaAgSb2 and YAgSb2 which exhibit a semimetallic character. The dHvA results have been compared with the results of the energy band calculations. It was concluded that the 4f electron is mainly localized and that the Fermi surface of CeAgSb2 is similar to tha...