NQR Study Research Articles

NQR and NMR Studies of Spin Dynamics in High Tc Superconducting Cuprates

Abstract Recent NQR and NMR studies of Cu spin dynamics in metallic YBa2Cu3O6+x are reviewed. The Cu nuclear relaxation rates are shown to be inconsistent with weak correlation (band) theory and the Korringa relation, but the Cu spins retain important characteristics of itinerancy. These include pairing of the Cu d-spins in the superconducting state and strong sensitivity of the Cu spin dynamics to changes in carrier concentration associated with variation of the oxygen content. Samples of reduced oxygen content (Tc = 60 K) are found to contain a high concentration of Cu+ Cu(1) sites associated with "full chain-empty chain" vacancy ordering. These samples also exhibit remarkable precursive suppression of planar Cu(2) nuclear relaxation above Tc .

NQR and Phase Transitions in Hexachlorocyclopropane Crystal

Abstract 35Cl NQR and DSC studies on phase transitions in hexachlorocyclopropane (HCCP), C3Cl6 , are reported. It is found that HCCP has three solid phases: A high temperature disordered phase (Phase I) above 301 K (no NQR spectrum was observed); a metastable phase (Phase II), which exhibited 6 NQR lines from 77 to 270 K; a low temperature phase (Phase III) in which a 24-multiplet of 35Cl NQR lines at 77 K, the most complex multiplet spectrum ever reported was observed. DSC measurement shows a A-type transition at 301 K and a broad transition of very slow rate at 285 K. The structure and mechanism of phase transitions in HCCP crystal are discussed.

Cu NQR Studies of the Superconductors YBa2Cu3Ox and YBa2Cu4O8

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.

NQR Studies of Atomic Arrangements and Chemical Bonding in Glasses

Abstract A very high sensitivity continuous wave NQR spectrometer was developed to detect pure NQR transitions at low frequencies (down to 200 kHz). A signal-to-noise ratio of more than 100 to 1 has been achieved at about 1.36 MHz for crystalline B 2 0 3 . Two large n B responses have been found in vitreous B 2 0 3 (NMR detected only one site) with linewidths of less than 30 kHz. 27 A1 NQR spectra were obtained for OC-A1203 (Corundum), the mineral andalusite (a form of A1203 • Si0 2), and a glass having the composition of anorthite (CaO • A1203 • 2Si0 2).

Zeeman NQR Studies on Powdered Bromine Compounds Having Small η

Abstract The Zeeman NQR of 79 Br and 81Br in samples having relatively small r\ was studied on several bromine compounds which were in the powder or polycrystal state. The absorption lines were detected in the integral form by the bridge circuit. When a static magnetic field was applied, the line shapes were broadened and usually two dips appeared symmetrically at both sides of the zero field line. The values of η were estimated from the patterns of the dips. For compounds such as NaBrO3 , however, as expected no dips were observed.

ChemInform Abstract: NMR and NQR Studies in High‐Tc Oxides: Yttrium Barium Copper Oxide, YBa2Cu3Oy (y = 6.0‐6.91)

ChemInformVolume 21, Issue 3 Reviews ChemInform Abstract: NMR and NQR Studies in High-Tc Oxides: Yttrium Barium Copper Oxide, YBa2Cu3Oy (y = 6.0-6.91) H. YASUOKA, H. YASUOKA Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorT. SHIMIZU, T. SHIMIZU Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorT. IMAI, T. IMAI Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorS. SASAKI, S. SASAKI Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorY. UEDA, Y. UEDA Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorK. KOSUGE, K. KOSUGE Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this author H. YASUOKA, H. YASUOKA Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorT. SHIMIZU, T. SHIMIZU Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorT. IMAI, T. IMAI Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorS. SASAKI, S. SASAKI Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorY. UEDA, Y. UEDA Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this authorK. KOSUGE, K. KOSUGE Inst. Solid State Phys., Univ. Tokyo, Tokyo 106, Jap.Search for more papers by this author First published: January 16, 1990 https://doi.org/10.1002/chin.199003320Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue3January 16, 1990 RelatedInformation

Transition from Local Moment to Fermi Liquid State in YbInCu4-Cu NQR Study-

Etude de la transition de valence de premier ordre. Determination de la temperature de transition a partir des analyses de la frequence de resonance et du temps de relaxation spin-reseau

NQR and NMR study of Bi (Pb) Sr Ca Cu O ceramic superconductors

Abstract Two Cu quadrupole resonances were found in the frequency range 15–29 MHz for the 2212 and 2223 phases, arising from Cu nuclei located at Cu sites with pyramidal and square oxygen environments.

14N NQR study of the structural phase transitions in NH4NO3

The temperature dependences of the14N nuclear quadrupole resonance frequencies have been measured in phases II, III, IV and V of ammonium nitrate with the help of the1H−14H nuclear quadrupole double resonance technique. The experimental results are related to the proposed crystal structures and disorder in the various crystallographic phases.

NMR and NQR studies in high-T c oxides: YBa2Cu3O y (6.0≤y≤6.91)

The NQR and NMR techniques have been utilized to characterize the local oxygen coordination of inequivalent Cu sites and the electronic properties in both the normal and superconducting states of YBa2Cu3Oy (6.0<-y≤6.91). The distinct NQR lines associated with the different oxygen-coordinated Cu sites, hence the locally differentiated charged states, have been observed. The degree of charge differentiation at the Cu(2) plane sites was found to be increased with decreasingy from 6.91, which might be related with the decrease ofT c. An anomalous temperature dependence of Cu nuclear spin-lattice relaxation timeT 1 has been observed for both the Cu(1) chain and Cu(2) plane sites fory=6.91 and it is discussed in connection with antiferromagnetic spin fluctuations in the normal state.

NQR study of complexes between p-dichlorobenzene and some aromatic π acceptors

The charge-transfer complexes of p-dichlorobenzene (PDB) with some aromatic π acceptors such as m-nitrobenzaldehyde (MNB), picric acid (PA), p-nitrobenzoic acid (PNB), and m-dinitrobenzene (MDNB) were prepared by slowly adding the acceptor to the molten donor and then cooling the mass to 15°C. The NQR frequencies of these complexes were measured at room temperature. Contrary to the theoretical prediction, the NQR shift is positive, indicating that the NQR shift in donor-acceptor complexes is indirectly related to the charge-transfer interaction. Bond properties are discussed in terms of frequency shift.

Structures of Some Derivatives of Chloral. An X‐Ray and NQR Study

AbstractCrystal structures of the stable and a metastable phases of 2,4‐bis(trichloromethyl)‐benzo‐1,3‐dioxine‐6‐carboxylic acid (TMB‐COOH) and 2,4‐bis(trichloromethyl)‐benzo‐1,3‐dioxine‐6‐amine (TMB‐NH2) were determined at room temperature. Crystal data are as follows; TMB‐COOH (stable): monoclinic, space group C52h‐P21/n, a = (1052.6 ± 0.2) pm, b = (2582.2 ± 0.4) pm, c = 598.7 ± 0.3) pm, β = 99.86° ± 0.02°, R = 0.053; TMB‐COOH (metastable): monoclinic,space group C52h‐P21/c, a = (577.5 ± 0.5) pm, b = (2087.2 ± 1.1) pm, c = (1318.6 ± 0.7) pm, β = 91.98° ± 0.06°, R = 0.098; TMB‐NH2: orthorhombic, space group C92v‐Pna21, a = (2539.0 ± 0.2) pm, b = (1005.1 ± 0.1) pm, c = (566.7 ± 0.1) pm, R = 0.049. Disorder of hydrogen atom in the OH ··· O hydrogen bond system was found for the cyclic dimers of TMB‐COOH in both phases. Judging from the molecular structures determined, chloral hydrate and 4‐substituted phenols seem to react in a stereospecific way to give a single conformer found in these crystals. The 35Cl NQR spectra of TMB‐COOH, TMB‐NH2 and related compounds were measured in the range 77 ≦ T/K ≦ 400. The temperature dependence of the NQR spectra showed that the potential barrier hindering the reorientation of the group is considerably different for the two nonequivalent CCl3 groups in a molecule. Atom‐atom potential calculations based on the crystal data showed that the difference is of intermolecular nature. The NQR frequencies calculated from the orbital populations obtained by the CNDO/2 MO method are consistent with the observed one.

ChemInform Abstract: NMR and NQR Studies in Yttrium Barium Copper Oxide (YBa2Cu3O7‐δ)

ChemInformVolume 20, Issue 7 Reviews ChemInform Abstract: NMR and NQR Studies in Yttrium Barium Copper Oxide (YBa2Cu3O7-δ) D. BRINKMANN, D. BRINKMANN Phys.-Chem. Inst., Univ. Zuerich, CH-8057 Zuerich, Switz.Search for more papers by this author D. BRINKMANN, D. BRINKMANN Phys.-Chem. Inst., Univ. Zuerich, CH-8057 Zuerich, Switz.Search for more papers by this author First published: February 14, 1989 https://doi.org/10.1002/chin.198907354Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue7February 14, 1989 RelatedInformation

Evidence of magnetic order of Cu moments in the superconducting and normal region of La2−Sr CuO4: Observation of Cu-NQR for 0.12≦x≦0.40

The observation of Cu-NQR in La2−xSrxCuO4 revealed that the spectra were splitted into two peaks at low temperatures and that its separation decreased with increasing x. This fact indicates that the well-defined hyperfine field due to magnetic ordering of Cu moments exists in the superconducting and normal metallic regions. The nuclear spin-lattice relaxation rate, 1/T1 of the Cu spectra is suppressed apparently by the superconducting energy gap for x≦0.20, while its temperature dependence obeys the Korringa relation for the normal region of x≧0.25. The nuclear spin-spin relaxation rate, 1/T2 increases proportionally with increasing hyperfine field, indicating the dominant indirect unclear spin coupling via virtual excitation of antiferromagnetic spin waves. The coexistence of superconductivity and the magnetic order of Cu d-electrons with a tiny moment is demonstrated by the NQR study in the La-Sr-Cu-O system

The temperature dependence of 35Cl NQR spectrum and study of spin—lattice relaxation times in chloral hydrate

The temperature investigation of nuclear quadrupole spin—lattice relaxation times in chloral hydrate above 290 K revealed the presence of an additional mechanism of relaxation. Its activation energy is 14.5 kcal mol −1 which is almost 6 kcal mol −1 greater than the energy corresponding to the hindered rotation of the CCl 3 group. We propose this additional mechanism to be the breaking of hydrogen bonds and translational diffusion of water molecules.

NQR investigation on ThBr 4 and instrumentation

The results of a recent NQR study of ThBr 4 and a brief survey of earlier work are presented. The temperature dependence of NQR frequencies of the α and β polymorphs is described. The line shape in the incommensurate phase, determination of the transition temperature, nuclear relaxation in the normal phase, far from and near the I transition, and strong phason relaxation in the I phase are also discussed.

NQR study of high-pressure deformation of the hydrogen bond potential

A variational correlated ground state wavefunction theory is employed for predicting and interpreting the pressure dependence of NQR frequency and isotope shift for several deuterated and undeuterated hydrogen bonded crystals. The evolution of the hydrogen bond potential with increasing pressure and the effects of deuterium isotope substitution on the quantum-fluctuation-driven phenomena are discussed. NQR-spectra parameters are strongly dependent on the bond length involved as well as the mass of tunneling particle. The correlation between the magnitude of geometric isotope effect and the NQR-frequency isotope shift as well as the value of pressure coefficients δν NQR/δ p have been found and explained on the basis of ground-state variational theory in terms of microscopic parameters of a compressed single hydrogen bond.

35Cl NQR studies on molecular complexes at low temperature

35Cl NQR frequencies were taken for chloranil and a few complexes of chloranil with aromatic hydrocarbons at liquid nitrogen temperature. The different lines are assigned to different geometrical arrangements.

NQR STUDY OF COPPER IN REBa2Cu3O7-y

NQR STUDY OF COPPER IN REBa₂Cu₃O_7-y

NMR and NQR studies of copper oxide superconductors (invited)

6 3 , 6 5Cu NMR and NQR measurements reveal remarkably different electronic character at the Cu(1) chain and Cu(2) plane sites in YBa2Cu3O7.0. In the normal state, spin-lattice relaxation rates at both sites are strongly enhanced relative to estimated d-band Korringa (T1) rates, but have sharply different temperature dependencies. Moreover, T1 anisotropy is greater than an enhanced Korringa model can account for. Below Tc, the temperature dependencies reveal significantly different spectra for quasiparticle excitation at the two sites with the strongest apparent energy gap occurring for the planar Cu(2) sites. At reduced oxygen content (YBa2Cu3O6.7) the relaxation at the Cu(1) sites is only slightly (∼30%) less than observed for YBa2Cu3O7.0 while the rates for the resonance at the frequency of the Cu(2) sites in YBa2Cu3O7.0 exhibit a large (∼2000 ×) decrease for a minority of planar Cu(2) sites indicates that these sites are electronically inactive. NMR shift measurements are used to analyze the susceptibility of YBa2Cu3O7.0 and obtain an upper limit for the electronic density of states.