Cu NQR Studies of the Superconductors YBa2Cu3Ox and YBa2Cu4O8

1990 ◽  
Vol 45 (3-4) ◽  
pp. 393-400 ◽  
Author(s):  
D. Brinkmann
Keyword(s):  
Pressure Dependence ◽  
Oxygen Deficiency ◽  
Relaxation Times ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Temperature And Pressure ◽  
University Of Zurich ◽  
The University ◽  
Knight Shifts

Abstract The paper reviews some copper NQR studies in the superconductors YBa2Cu3Ox and YBa2Cu4O8 performed at the University of Zürich. The following topics are discussed: the temperature and pressure dependence of the NQR frequencies; relation between linewidths and oxygen deficiency; the determination of the electric field gradients (EFG) and Knight shifts at the copper sites; discussion of some calculations of the EFG tensors; measurements of the various relaxation times in all phases. The results obtained in both structures are compared; possible interpretations are discussed.

Probing the Electronic Structure of Y-Ba-Cu-O Superconductors by Copper NQR/NMR

1992 ◽  
Vol 47 (1-2) ◽  
pp. 1-6 ◽  
Author(s):  
D. Brinkmann
Keyword(s):  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Yield Information ◽  
Temperature And Pressure ◽  
University Of Zurich ◽  
The University ◽  
Knight Shifts ◽  
Substituted 1

abstractThe paper discusses some NQR/NMR studies performed on Y-Ba-Cu-O superconductors at the University of Zürich. It is shown how the resonance methods can yield information on electronic properties of quite different character. The review deals with: (1) the temperature and pressure dependence of Cu NQR frequencies in YBa2Cu4O8(1-2-4); (2) an NQR study of the properties of Ca substituted 1-2-4; (3) the temperature dependence of the Cu Knight shifts in 1-2-4; (4) the NMR of plane Cu2 in the paramagnetic state of YBa2Cu3O6 ; (5) the dependence on temperature, pressure and orientation of the Cu spin-lattice relaxation in 1-2-4.

scholarly journals Cluster Calculations of Hyperfine Interactions in Superconducting Copper Compounds

2000 ◽  
Vol 55 (1-2) ◽  
pp. 247-255
Author(s):  
P. F. Meier ◽  
T. A. Claxton ◽  
P. Hüsser ◽  
S. Plibersek ◽  
E. P. Stoll
Keyword(s):  
Copper Ions ◽  
Hyperfine Interactions ◽  
Electric Field Gradients ◽  
Copper Compounds ◽  
Field Gradients ◽  
Cluster Calculations ◽  
Spin Polarized ◽  
Quadrupole Resonance ◽  
University Of Zurich ◽  
The University

This paper discusses first-principles cluster investigations on the electronic structure of YBa2Cu3Ü7 and La2CuO4 performed at the University of Zürich. In particular, electric field gradients have been calculated at the copper sites and their dependence on applying uniaxial strain is studied. Magnetic hyperfine interactions have been evaluated from spin-polarized calculations, and the transfer of spin density from neighboring copper ions is explained. An interpretation is given of the nuclear quadrupole resonance spectra in doped La2CuO4.

scholarly journals Effect of Temperature and Pressure on Segmental Relaxation in Polymethylphenylsiloxane

2003 ◽  
Vol 76 (5) ◽  
pp. 1106-1115 ◽  
Author(s):  
S. Pawlus ◽  
S. J. Rzoska ◽  
J. Ziolo ◽  
M. Paluch ◽  
C. M. Roland
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Pressure Dependence ◽  
Activation Volume ◽  
Relaxation Times ◽  
Effect Of Temperature ◽  
Loss Peak ◽  
Glass Transition Temperatures ◽  
Segmental Relaxation ◽  
Temperature And Pressure

Abstract Segmental relaxation in a series of polymethylphenylsiloxanes (PMPS) was studied using dielectric spectroscopy. The measurements covered a temperature range of more than 40 deg at pressures from ambient to 115 MPa. The results confirmed that the shape of the loss peak is independent of temperature, pressure and molecular weight. Consequently, the Tg -scaled dependence of the relaxation times was also independent of molecular weight. The pressure dependence of the relaxation times was characterized by means of the activation volume. This quantity changes markedly with pressure at a given temperature. However, the activation volume at the respective glass transition temperatures of the PMPS are essentially invariant to molecular weight. Finally, we measured the dependence of Tg on pressure, with the results well-described by the Andersson equation.

The measurement of the apparent nuclear spin-spin relaxation times of N.Q.R. signals in the ultra-high-frequency region

1981 ◽  
Vol 34 (3) ◽  
pp. 641 ◽  
Author(s):  
PJ Bryant ◽  
S Hacobian
Keyword(s):  
Spin Relaxation ◽  
High Frequency ◽  
Relaxation Times ◽  
Principal Component ◽  
Coaxial Line ◽  
Crystal Defects ◽  
Electric Field Gradients ◽  
High Frequency Region ◽  
Pulse Detection ◽  
Field Gradients

Apparent spin-spin relaxation times, T2*, for the 127I nuclear quadrupole resonances of a series of substituted iodobenzenes were measured by the Doolan-Hacobian double-pulse detection technique. A coaxial line oscillator capable of operation to 800 MHz was used to obtain the signals of the higher frequency transitions. It is shown that the ratio of the T2* measurements of the lower to the upper transition in spin 5/2 systems is of the order of two. This is in accordance with the assumption that the broadening is mainly electrical in nature and arises from the spread in the principal component of the electric field gradients produced by crystal defects.

The pressure dependence of the dehydration of gypsum to bassanite

1987 ◽  
Vol 51 (361) ◽  
pp. 453-457 ◽  
Author(s):  
J. D. C. McConnell ◽  
D. M. Astill ◽  
P. L. Hall
Keyword(s):  
Elevated Temperature ◽  
Experimental Determination ◽  
Volume Change ◽  
Pressure Dependence ◽  
Thermodynamic Data ◽  
Dehydration Reaction ◽  
Temperature And Pressure ◽  
The Stability ◽  
Very High

AbstractA new experimental determination of the stability relationships for the dehydration of gypsum to the hemihydrate mineral bassanite at elevated temperature and pressure is described. The experimental method used depends on the observation of very small changes in pressure on the onset of reaction due to the potential volume change in the reaction. The technique yields P-T data of very high precision for this dehydration reaction, and the method is likely to be of use for other reactions. The experimental P-T results have been compared with those calculated from existing thermodynamic data for this reaction.

scholarly journals Temperature Variation at Solid-Fluid Interface of Thin Film Lubricated Contact Problems

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 922
Author(s):  
Szabolcs Szávai ◽  
Sándor Kovács
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Pressure Dependence ◽  
Hydrodynamic Pressure ◽  
Contact Problems ◽  
Element Formulation ◽  
Temperature And Pressure ◽  
Non Linear System ◽  
Element Method

Many calculating methods have been already developed for solving contact problems of parts such as gears, cams, and followers under fluid film lubrication conditions considering the temperature and pressure dependence. Similarly, the determination of the elasto-hydrodynamic pressure distribution the processes taking place in the lubricant and the contacting bodies, as well as in their environment, have to be dealt with simultaneously for the determination of the temperature field. A system of equation for the modelling of thermo-elastohydrodynamic lubrication between two contacting bodies containing hydrodynamic, thermodynamic, and strength problems is a highly non-linear system which becomes even more so if the temperature and pressure dependence of the material properties are considered. To solve this system, scientists started to use the finite element formulation in the 1960s and it was found to be a promising and reliable method. Earlier, the lubrication analysts used only the h-version finite element method (h-FEM) till 1991, when the first usage of the p-version finite element method (p-FEM) was published in the literature. In order to reduce the problem, in case of point or line contact, the contact bodies can be handled as semi-infinite ones. Following this simplification that had been successfully applied for the gap size determination, a substructure model was defined using analytical solution of the moving heat source. Instead of an iterative way between the solid and fluid problem, in this paper we present an efficient solution when thermal model for lubricant and surfaces were coupled and solved by a direct numerical method in one step.

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