Showing papers on "Transition temperature published in 1983"
IBM1
TL;DR: In this article, the temperature dependence of the optic index of refraction, n(T), at several wave lengths in two ferroelectric compounds that have the simple perovskite ABO3 structure was investigated.
585 citations
IBM1
TL;DR: In this article, the first unambiguous observation of superconductivity in a sulphur-donor organic system was made, where BEDT-TTF exhibits a first-order metal-insulator transition, postulated to result from a change in the arrangement of the anions which are ordered at room temperature.
Abstract: Evidence for superconductivity in (BEDT-TTF) 4 (ReO 4) 2 [where BEDT-TTF is bis(eth-ylenedithiolo)tetrathiafulvalenel near 2 K for pressures above 4 kbar is reported. This is the first unambiguous observation of superconductivity in a sulphur-donor organic system. At higher pressures the transition temperature decreases rapidly, dT c,/dP~- 0.3 K/kbar. At low pressures this material exhibits a first-order metal-insulator transition, postulated to result from a change in the arrangement of the anions which are ordered at room temperature.
273 citations
TL;DR: In this article, the superconducting transition temperature, upper critical field, and magnetic susceptibility have been measured in four binary metallic glass systems: Co-Zr, Co-CoZr and FeZr.
Abstract: The superconducting transition temperature, upper critical field, and magnetic susceptibility have been measured in four binary metallic glass systems: Cu-Zr, Ni-Zr, Co-Zr, and Fe-Zr For each alloy system, a full and continuous range of Zr-rich compositions accessible by melt spinning has been examined For Cu-Zr, the range is $075gxg030$; for Ni-Zr, $080gxg030$; for Co-Zr, $080gxg048$, and for Fe-Zr, $080gxg055$ ($x$ being the concentration of Zr in at%) The results show clearly the influence of spin fluctuations in reducing the superconducting transition temperature The data have been successfully analyzed using a modified form of the McMillan equation together with expressions for the Stoner enhanced magnetic susceptibility and the Ginsburg-Landau-Abrikosov-Gor'kov expression for the upper critical field
216 citations
TL;DR: In this paper, the effects of vortex-unbinding phase transition on the properties of a square lattice of superconducting weak links are discussed, and formulas relating bulk static quantities such as the penetration depth and transition temperature to single-junction parameters are given, as well as formulas for the current and temperature-dependent resistance.
Abstract: The effects of a vortex-unbinding phase transition on the properties of a square lattice of superconducting weak links are discussed. Formulas relating bulk static quantities such as the penetration depth and transition temperature to single-junction parameters are given, as well as formulas for the current- and temperature-dependent resistance. Except for temperatures very near the transition temperature, these results can differ significantly from the continuum results of Halperin and Nelson, and thus may be more appropriate for description of junction arrays and some granular films.
211 citations
TL;DR: In this paper, the role of cyclization in determining the temperature adaptation is studied on three lipid samples presenting four, five and six cyclopentane rings per molecule, respectively, and both sets of measurements indicate the presence of thermal transitions, three in the hydrated compounds, two in the dry system.
170 citations
TL;DR: In this paper, the tensile behavior of linear polyethylene was examined over a wide range of temperatures, and it was found that the temperature of the ductile-brittle transition was markedly different for different samples.
Abstract: The tensile behaviour of linear polyethylene was examined over a wide range of temperatures. Samples were prepared from low and medium molecular weight polymer with different morphologies, by varying the initial crystallization conditions. It was found that the temperature of the ductile-brittle transition was markedly different for different samples. In particular, low molecular weight polymer crystallized at a low degree of of supercooling, showed brittle behaviour over most of the temperature range, with a ductile-brittle transition near to room temperature. Rapidly quenched material, where the degree of supercooling is high, showed a very low ductile-brittle transition temperature, especially in high molecular weight polymer. The reasons for these differences in behaviour are discussed both at a phenomenological level and in terms of known structural differences between the different materials examined.
154 citations
TL;DR: In this paper, low-frequency techniques are used to examine the predictions of the equilibrium Kosterlitz-Thouless theory of the vortex-pair unbinding transition in indium/indium-oxide composite superconducting thin films.
Abstract: Low-frequency techniques are used to examine the predictions of the equilibrium Kosterlitz-Thouless theory of the vortex-pair unbinding transition in indium/indium-oxide composite superconducting thin films. The renormalized superfluid density obtained from independent measurements of the kinetic inductance and the exponent of the current-dependent resistance are in agreement. At the transition temperature ${T}_{c}$, the critical value of the superfluid density agrees with theory for a finite measurement length. Experimental sensitivity is such that the resistance near ${T}_{c}$, measured to be about 9 orders of magnitude below the normal resistance, is explained by the motion of a single thermally excited free vortex in a superfluid background renormalized by bound-vortex pairs. The corresponding critical magnetic field for flux entry is also measured. The resistance of the thermally excited free-vortex plasma and the correlation length above the transition temperature obey the qualitative prediction of the theory. Nonuniversal constants in the renormalization-group theory are obtained from the experiment and are found to be sample dependent.
134 citations
TL;DR: In this article, a simple model is used to describe the nucleation of bubbles during a first-order relativistic cosmological phase transition, and it is shown that the characteristic size of bubbles when the transition ends is smaller than the Hubble length by a factor of at least 1/4 ln[TP/Tc], where TP is the Planck temperature and Tc is the transition temperature.
118 citations
TL;DR: In this article, the authors reported non linear transport properties below the metal-insulat transition temperature T° = 263 K in the halogened metal transition tetrachalcogenide (TaSe4)2I.
110 citations
TL;DR: In this article, the glass transition temperature of polystyrene has been studied by DSC Glass transition, well known for macromolecules, has been observed up to the monomer.
Abstract: Glass transition temperature of polystyrene has been studied by DSC Glass transition, well known for macromolecules, has been observed up to the monomer Measurements of the change in heat capacity ΔCp at Tg were carried out and a relationship between \(\frac{{\Delta Cp}}{T}\) and \(\overline {Dp}\) has been found The results have been interpreted as a modification of interaction occuring at \(\overline {Dp}\)≃25
102 citations
TL;DR: A quantitative analysis of the relaxation in terms of thermodynamic relationships between specific heat, thermal-expansion coefficient, and compressibility showed that more than 90% of the total endothermic heat of the transition arises from the latent heat.
TL;DR: In this paper, the transition temperature of [Fe(phen) 2 (NCS) 2 ] measured by susceptibility measurements in an applied field of 1 T shifts by −0.11 − 0.04 K when the field is increased to 5.5 T.
TL;DR: In this paper, the surface hyperfine field rapidly decreased with increase of temperature but the Morin transition took place at the same transition temperature as the bulk crystal and the surface was very thinly coated with 57 Fe.
TL;DR: In this article, a method based on X-ray rocking curves was developed to measure subgrain misorientation angles of crept specimens and it was concluded that a cross-slip controlled mechanism cannot control below the transition temperature.
Abstract: Creep tests in the high temperature range (0.68 Tm-0.94 Tm, where Tm is the melting temperature) have been performed on high purity tin single crystals with the [100] direction as the tensile axis. Above the transition temperature, about 0.84 Tm (150 °C), the creep activation energy was found to be almost equal to the self diffusion energy. Below the transition temperature the creep activation energy is about half of the self diffusion energy and has a value of the order expected for dislocation pipe diffusion. A method based on X-ray rocking curves was developed to measure subgrain misorientation angles of crept specimens. The average subgrain misorientation angles for specimens crept at 70 °C and 100 °C increased continuously with creep strain at rates a factor of 20 to 40 smaller than that predicted by a cross-slip controlled process. The average subgrain misorientation angles at a given strain decrease slightly with increasing temperature. However, no abrupt change of the angle was observed at the transition temperature. It was concluded that a cross-slip controlled mechanism cannot control below the transition temperature. Instead, our results lend support to Sherby and Weertman’s argument that dislocation climb controls creep over the entire high temperature regime.
TL;DR: In this paper, the influence of ordinary impurities on the superconducting transition in a quasi-one-dimensional metal was studied in a self-consistent field (BCS) approximation, and it was shown that depending on the properties of the electron-electron interaction, singlet or triplet superconductivity may appear.
Abstract: The influence of ordinary impurities on the superconducting transition is studied in a quasi-one-dimensional metal. Superconductivity is considered in a self-consistent field (BCS) approximation. It is shown that, depending on the properties of the electron-electron interaction, singlet or triplet superconductivity may appear. Impurities do not influence the critical temperature in the singlet case but destroy the triplet superconductivity. The concentration dependence of the critical temperature in the triplet case is in qualitative agreement with the experimental results for irradiated quasi-1d superconductors; therefore triplet superconductivity may be supposed in these systems. The superconducting current is calculated in the vicinity of the transition temperature and hence the longitudinal dielectric constant for not too high frequencies.
TL;DR: This article examined the adsorption of Na on Ru(001) as a function of coverage and temperature using LEED to determine the adlayer structure and thermal desorption spectroscopy to characterize binding kinetics and relative Na coverages.
TL;DR: In this paper, the magnetic phase transition in materials with exchange disorder (amorphous ferromagnets, spin glasses) is discussed and a molecular field theory with correlations in space and time is developed, which relates deviations from the mean field behavior to the interplay between the temperature dependent thermal correlations in the spin system and the spatial fluctuations of the material.
TL;DR: The electrical resistance of a linear chain metal Nb3Te4 was measured from 1.3 to 320 K and the residual resistance ratio R(300 K ) R(4.2 K ) is about 3.8.
TL;DR: In this article, the dependence of superconducting transition temperature on the thickness of Nb films deposited upon several kinds of substrates by means of rf sputtering was studied in search of rudimental data necessary in fabricating variable thickness microbridge type Josephson junctions.
Abstract: Dependence of superconducting transition temperature on the thickness of Nb films deposited upon several kinds of substrates by means of rf sputtering was studied in search of rudimental data necessary in fabricating variable thickness microbridge type Josephson junctions. The transition temperature was found to lower with the decrease of Nb film thickness. The lowering characteristics of the transition temperature were found to vary in accordance with whether the substrate surface was amorphous or crystalline. The cause of the variance was studied on thin films with the aid of x‐ray diffraction pattern analysis and measurement of film resistance.
TL;DR: In this paper, the spectral distribution of magnetic fluctuation scattering from metallic nickel has been studied above the Curie temperature with unpolarized and polarized neutrons, and it was shown that the main part of the magnetic scattering above T/sub c/ does not come from the spin-wave ridge in (..omega.., q) space but from a spectral part centered at zero energy with a broad energy distribution.
Abstract: The spectral distribution of the magnetic fluctuation scattering from metallic nickel has been studied above the Curie temperature with unpolarized and polarized neutrons. The present measurements confirm previous results of a spin-wave-like mode above T/sub c/. It is shown, however, that the main part of the magnetic scattering above T/sub c/ does not come from the spin-wave ridge in (..omega.. , q) space but from a spectral part centered at zero energy with a broad energy distribution.
TL;DR: In this paper, preliminary results of the neutron diffraction and inelastic scattering studies on the quasi-one-dimensional conductor K0.3MoO3 with a metal-insulator transition are reported.
Abstract: Preliminary results of the neutron diffraction and inelastic scattering studies on the quasi-one-dimensional conductor K0.3MoO3 with a metal-insulator transition are reported. The temperature dependence of the intensity of the superlattice reflection is found to be approximately described by a simple equation. A phonon mode seems to have an almost complete softening at the transition temperature Tc. The existence of the large central peak in the inelastic spectra above Tc suggest that the local correlation between electrons is very strong. The wavevector of the charge density wave smoothly approaches the commensurate one, as the temperature is lowered and lock-in transition does not occur down to T approximately=6K.
TL;DR: An extension of the McMillan and Nakanishi and Shiba (1977) models of charge-density-wave formation which fully reflects the space-group symmetry of the $1T\ensuremath{-}\mathrm{Ta}{\mathm{S}}_{2}$ structure is presented in this paper.
Abstract: An extension of the McMillan (1975) and Nakanishi and Shiba (1977) models of charge-density-wave formation which fully reflects the space-group symmetry of the $1T\ensuremath{-}\mathrm{Ta}{\mathrm{S}}_{2}$ structure is presented. The model allows an incommensurate $c$-axis wave vector immediately below the normal to incommensurate transition temperature, and a $c$-axis wave-vector lock-in transition at a lower temperature. The model also allows a number of different commensurate phases characterized by different charge-density-wave stacking configurations. A triple-honeycomb domain structure is described.
TL;DR: In this paper, the mechanism of the ferroelectric phase transition of CsD 2 PO 4 was investigated by examining the crystal structures determined by X-ray structure analysis at seven different temperatures above and below the transition temperature T c.
Abstract: The mechanism of the ferroelectric phase transition of CsD 2 PO 4 was investigated by examining the crystal structures determined by X-ray structure analysis at seven different temperatures above and below the transition temperature T c . The PO 4 group has two equilibrium arrangements in the paraelectric phase while only one of them remains in the ferroelectric phase. The thermal amplitude of the D atom which forms a one-dimensional chain along the ferroelectric b -axis reduces drastically at T c with decreasing temperature. These results are well described on the basis of the mechanism of the order-disorder type phase transition.
TL;DR: In this paper, single crystals of tetramethylammonium tetrabromomanganate {N(CH 3 ) 4 } 2 -MnBr 4 were grown, and the phase transition was studied by dielectric measurements.
Abstract: Single crystals of tetramethylammonium tetrabromomanganate {N(CH 3 ) 4 } 2 -MnBr 4 were grown, and the phase transition was studied by dielectric measurements. The crystal shows a phase transition at 3.5°C. The transition temperature increases linearly with increasing hydrostatic pressure with a slope of 0.185 deg MPa -1 . Similarity of the lattice parameters, dielectric properties, and pressure coefficient of the transition temperature to those found in {N(CH 3 ) 4 } 2 ZnBr 4 and {N(CH 3 ) 4 } 2 CoBt 4 compounds suggests that there is a common mechanism of the phase transitions in these bromide compounds.
TL;DR: In this paper, the concentration dependence of the ferroelectric transition temperature Tc of single crystals of the solid solution Tris-sarcosine calcium chloride1-x bromidex is studied experimentally by measurement of the static dielectric constant eb and described by the empirical relation Tc(x) = Tc (0) (1 x/xcc)1/2.
Abstract: The concentration dependence of the ferroelectric transition temperature Tc of single crystals of the solid solution Tris-sarcosine calcium chloride1-x bromidex is studied experimentally by measurement of the static dielectric constant eb and described by the empirical relation Tc(x) = Tc(0) (1 x/xcc)1/2. The Ising model with transverse field and the model of coupled anharmonic oscillators are used to explain the concentration dependence of the transition temperature Tc. The influence of quantum fluctuations is discussed.
TL;DR: In this article, the conductivities of a single crystal and a sintered pellet of Li 2 O were measured in argon atmosphere by the two-terminal technique with an ac Wheatstone bridge in the temperature range 300-1150°C.
TL;DR: In this article, the heat capacity of aqueous suspensions of dipalmitoylphosphatidylcholine has been measured near the pretransition and main transition.
Abstract: By an ac calorimeter the heat capacity of aqueous suspensions of dipalmitoylphosphatidylcholine has been measured near the pretransition and main transition. The anomaly at the main transition exhibits a sharp divergence, i.e., the fluctuation at the transition is certainly dominant, although they undergo first-order transition. The pseudo-critical behavior is analyzed in terms of critical-exponent expressions: α and α' are 0.40±0.05 and 0.4±0.1, respectively. Using Pippard's relation, the dependence of the transition temperature on pressure is discussed, which is almost consistent with that of the direct experiments. The anomaly at the pretransition observed by a differential scanning calorimeter is extremely reduced in ac calorimetry. This is due to the frequency dispersion of the heat capacity, since the relaxation at this transition is very long.
TL;DR: In this paper, a review of magnetically-ordered ternary and pseudoternary rare earth superconductors is presented, where the authors show that superconductivity coexists with antiferromagnetic order, but is destroyed by the onset of ferromagnetic ordering at a second transition temperature T c2 ≈ T M, where T M is the Curie temperature.
TL;DR: In this article, the influence of the external electric field on ferroelectrics exhibiting the incommensurate-commensurate phase transition is investigated within the Landau-type theory and the constant-amplitude approximation.
Abstract: The influence of the external electric field on ferroelectrics exhibiting the incommensurate-commensurate phase transition is investigated within the Landau-type theory and the constant-amplitude approximation. The temperature variation of the modulation period, the polarisation and the dielectric susceptibility are calculated. It is shown that finite fields preserve the character of the transition, but lead to a shift of the transition temperature. A comparison with experiments on Rb2ZnCl is presented. The possibility of a field-induced Lifshitz point in incommensurate ferroelectrics is discussed.
IBM1
TL;DR: In this paper, the authors summarize some of the recent measurements of the temperature dependence of the optic index of refraction, n(T), in several different classes of ferroelectrics and show that the crystals possess a local, randomly oriented, nonreversible polarization.
Abstract: We summarize some of our recent measurements of the temperature dependence of the optic index of refraction, n(T), in several different classes of ferroelectrics. The common thread between these different materials is that in all of them the translational symmetry is strongly broken. Far above the usual ferroelectric transition temperature Tc up to a temperature Td, we show that the crystals possess a local, randomly oriented, nonreversible polarization. Using a simple model for this behavior, we can account for it qualitatively and in some systems quantitively understand Td. We believe this model contains the basic physical understanding of ferroelectrics that have a diffusive phase transition.