89Y NMR SPECTRA AND RELAXATION IN UNDERDOPED AND OVERDOPED REGIMES OF SUPERCONDUCTING Ca-DOPED YBCO6 AND YBCO7

2003 ◽  
Vol 17 (04n06) ◽  
pp. 791-798
Author(s):  
P. CARRETTA ◽  
A. LASCIALFARI ◽  
A. RIGAMONTI ◽  
P. TEDESCO ◽  
F. TEDOLDI
Keyword(s):  
Knight Shift ◽  
Nmr Spectra ◽  
Spin Echo ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Antiferromagnetic Correlation ◽  
Experimental Findings

The results of a study of 89 Y NMR line shape and Knight shift, of the spin-echo dephasing time and of spin lattice relaxation time in Ca-doped YBCO compounds are presented. The underdoped and the overdoped regimes are achieved by means of Ca 2+ for Y 3+ substitutions in the parent antiferromagnet YBa 2 Cu 3 0 6.1 and in the chain-full YBa 2 Cu 3 0 7, respectively. The experimental findings are discussed in the light of models of localized Cu 2+ electrons and of delocalized Fermi-like carriers with antiferromagnetic correlation. Insights are obtained in regards of the density of states evolution with doping and of the occurrence, in the underdoped regime, of low-energy magnetic excitations causing a divergence of the relaxation rates on cooling, accompanied by a concurrent broadening of the NMR line. It is argued how a revision of the commonly accepted view for the microscopic magnetic properties in the YBCO family is required in order to attain a comprehensive justification of the variety of experimental data.

scholarly journals Inter-plane Coupling and Spin Gap -an NMR/NQR Look on Typical Properties of High-Temperature Superconductors

1996 ◽  
Vol 51 (5-6) ◽  
pp. 786-792
Author(s):  
D. Brinkmann
Keyword(s):  
Relaxation Time ◽  
Spin Echo ◽  
High Temperature Superconductors ◽  
Double Resonance ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Spin Gap ◽  
Spin Lattice

Abstract The paper discusses some NQR/NMR studies performed on Y-Ba-Cu-O superconductors at the University of Zürich. In particular, we review studies performed in Y2Ba4Cu7O15 by measuring various planar Cu NQR/NMR parameters: the spin-lattice relaxation time, the Knight shift and the indirect component of the Gaussian contribution to the spin-spin relaxation time. The temperature dependence of these parameters reveals a coupling between adjacent planes of a double plane. The existence of the inter-plane coupling has independently been confirmed by performing NQR Spin-Echo Double Resonance (SEDOR) experiments. The appearance of a spin gap seems to be the consequence of inter-plane coupling.

scholarly journals Dipolar induced spin-lattice relaxation in the myelin sheath: A molecular dynamics study

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Felix Schyboll ◽  
Uwe Jaekel ◽  
Francesco Petruccione ◽  
Heiko Neeb
Keyword(s):  
Myelin Sheath ◽  
Molecular Model ◽  
Membrane Surface ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Wide Range ◽  
Experimental Findings ◽  
Field Strengths

Abstract Interactions between hydrogen protons of water molecules and macromolecules within the myelin sheath surrounding the axons are a major factor influencing the magnetic resonance (MR) contrast in white matter (WM) regions. In past decades, several studies have investigated the underlying effects and reported a wide range of R1 rates for the myelin associated compartments at different field strengths. However, it was also shown that the experimental quantification of the compartment-specific R1 rates is associated with large uncertainties. The current study therefore investigates the longitudinal relaxation rates within the myelin sheath using a molecular dynamic (MD) simulation. For this purpose, a realistic molecular model of the myelin sheath was employed to determine the dipole-dipole induced R1 relaxation rate of the hydrogen protons at clinically relevant field strengths. The results obtained clearly reflect the spatial heterogeneity of R1 with a increased relaxivity of myelin water due to a reduced molecular mobility near the membrane surface. Moreover, the calculated R1 rates for both myelin water and macromolecules are in excellent agreement with experimental findings from the literature at different field strengths.

NQR and Neutron Diffraction in Scheelites

1992 ◽  
Vol 47 (1-2) ◽  
pp. 308-312 ◽  
Author(s):  
R. Julian C. Brown ◽  
E. Shortreed ◽  
Andrew J. Szabo ◽  
Brian M. Powell ◽  
Stephen N. Stuart
Keyword(s):  
Neutron Diffraction ◽  
Temperature Dependence ◽  
Structural Parameters ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Unit Cell ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Wide Range

AbstractMeasurements of the spin-lattice relaxation time for rhenium in KReO4 and NH4ReO4 are reported; relaxation rates are extremely fast due to the large quadrupole moment of Re. Calculations of the electric field gradient in KReO4 show that the EFG is a very sensitive function of the orientation of the anion in the unit cell as well as of the unit cell dimensions, and that geometrical effects make a major contribution to the temperature dependence. Neutron diffraction in these two salts has been employed to determine the temperature dependence of structural parameters over a wide range of temperature, and preliminary results are reported.

NMR Study of the Molecular Motion of Water in Natrolite

1974 ◽  
Vol 52 (21) ◽  
pp. 2164-2173 ◽  
Author(s):  
R. T. Thompson ◽  
R. R. Knispel ◽  
H. E. Petch
Keyword(s):  
Molecular Motion ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Nmr Study ◽  
History Of ◽  
Made In

The dynamics of water molecules in natrolite (Na2Al2Si3O10∙2H2O) were studied using proton magnetic resonance. At 4.2 K, rigid lattice values were observed for the proton second moment and line width and these quantities changed little up to 400 K. Between 300 and 460 K a narrower component of the proton line appeared, the relative intensity of which depended on the thermal history of the sample. The narrower component grew rapidly at the expense of the broader component as the temperature was increased above 460 K until only a narrow line (δH < 1 G) remained at 545 K. Spin lattice relaxation time measurements were made in the laboratory (T1) and rotating (T1ρ) frames. T1 decreased monotonically from 20 s at 77 K to 0.2 s at 435 K but did not reach a relative minimum. Relative minima in T1ρ were observed at 280 and 377 K for H1 = 4 G and the activation energies for the processes responsible for these minima were determined to be 8.6 ± 0.6 and 13 ± 2 kcal/mole respectively. Spin lattice relaxation rates based on 180° flips and other possible motions of the water molecules are discussed and compared to results obtained in other hydrates and zeolites.

NMR Studies on the Dynamics of Intercalated Water in Li-saponite

1997 ◽  
Vol 52 (12) ◽  
pp. 863-866 ◽  
Author(s):  
Shin'ichi Ishimaru ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Time ◽  
Nmr Spectra ◽  
Hydration Shell ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Rotational Freedom

The dynamics of intercalated water molecules in Li-saponite was studied by measurement of solid state 2H and 7Li NMR spectra and of the 2H spin-lattice relaxation time at 175 ~ 350 K. Only a single component was observed in the 2H spectra above 260 K, suggesting that the water hydrogens rapidly exchange their positions between various distinct environments. Analysis of the observed spectra suggests that the water molecules possess C2 rotational freedom at around 260 K and that the hydration shell around Li+ cations is highly symmetrical in the same temperature region

35Cl Quadrupole Relaxation Study on Cs2[Au(I)Cl2][Au(III)Cl4] and Cs2[Ag(I)Cl2][Au(III)Cl4]

2002 ◽  
Vol 57 (6-7) ◽  
pp. 348-352
Author(s):  
A. Ishikawa ◽  
M. Kurasawa ◽  
K. Kurasawa ◽  
A. Sasane ◽  
R. Ikeda ◽  
...  
Keyword(s):  
Spin Echo ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Quadrupole Relaxation ◽  
Spin Lattice ◽  
Three Samples ◽  
Two Samples ◽  
Relaxation Study ◽  
Line Widths

Two 35ClNQR spin echo signals, VQ1 = 17.28MHz (Au(I)-Cl) and VQ2 = 27.10MHz (Au(III)-Cl), have been observed at 77 K from two samples of Cs2[Au(I)Cl2][Au(III)Cl4] prepared differently. The resonances resulted at the same frequencies but with different line widths. Cs2[Ag(I)Cl2]- [Au(III)Cl4] yielded a singlet, VQ2 = 27.96 MHz, at 77 K. The three samples gave rise to ESR signals indicating the presence of paramagnetic Au(II) or Ag(II) sites with low concentration. 35ClNQR spin-lattice relaxation time T1Q measurements revealed that only the reorientational motions of the anions [Au(III)Cl4]− are exited at high temperatures.

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