Showing papers on "Nuclear quadrupole resonance published in 2001"
TL;DR: In this article, the temperature T dependence of the nuclear spin-lattice relaxation rate 1/T{sub 1} of {sup 115}In in the normal state indicates that CeCoIn{sub 5} is located just at an antiferromagnetic instability.
Abstract: We have carried out {sup 115}In and {sup 59}Co nuclear quadrupole resonance and nuclear magnetic resonance measurements on CeCoIn{sub 5} and CeIrIn{sub 5}. The temperature T dependence of the nuclear spin-lattice relaxation rate 1/T{sub 1} of {sup 115}In in the normal state indicates that CeCoIn{sub 5} is located just at an antiferromagnetic instability, and CeIrIn{sub 5} is in the nearly antiferromagnetic region. In the superconducting state, 1/T{sub 1} has no Hebel-Slichter coherence peak just below T{sub C} and a power-law T dependence (close to T{sup 3}) at very low temperatures, which indicates the existence of line nodes in the superconducting energy gap. The {sup 115}In (Ce-In plane) Knight shift in CeCoIn{sub 5} decreases for both parallel and perpendicular directions to the tetragonal c axis in the superconducting state, which shows that the spin susceptibility decreases in all directions. These results indicate that CeCoIn{sub 5} and CeIrIn{sub 5} exhibit non-s-wave even parity (probably d-wave) superconductivity.
190 citations
TL;DR: The nuclear quadrupole moment (NQM) of the Ipi = 3/2(-) excited nuclear state of 57Fe at 14.41 keV is determined from the large-scale nuclear shell-model calculations for 54Fe, 57Fe, and also from the electronic ab initio and density functional theory calculations including solid state and electron correlation effects for the molecules Fe(CO)(5) and Fe(C5H5)(2).
Abstract: The nuclear quadrupole moment (NQM) of the Ipi = 3/2(-) excited nuclear state of 57Fe at 14.41 keV, important in Mossbauer spectroscopy, is determined from the large-scale nuclear shell-model calculations for 54Fe, 57Fe, and also from the electronic ab initio and density functional theory calculations including solid state and electron correlation effects for the molecules Fe(CO)(5) and Fe(C5H5)(2). Both independent methods yield very similar results. The recommended value is 0.15(2) e b. The NQM of the isomeric 10+ in 54Fe has also been calculated. The new NQM values for 54Fe and 57Fe are consistent with the perturbed angular distribution data.
78 citations
TL;DR: In this article, a new nuclear quadrupole resonance (NQR) method was proposed for the detection of spin-1 nuclei, where the transition excited and directly detected is not irradiated at all.
43 citations
TL;DR: In this paper, the use of circularly polarized RF magnetic fields for excitation followed by detection of the resultant circular RF magnetization in I = 1 NQR to increase the fraction of nuclei excited and detected.
33 citations
TL;DR: The phase transition of Cs3Sb2I9, Cs 3Bi2Br9, and Cs1Sb 2I9 was investigated by 133C NMR and 127I NQR signals in this article.
Abstract: The phase transitions of Cs3Sb2I9 , Cs3Bi2I9 , and Cs3Bi2Br9crystals were investigated by 133Cs nuclear magnetic resonance. Cs3Bi2Br9was also studied by 87Br nuclear quadrupole resonance. The parameters of the Cs electric-field gradient tensors were determined. The phase transitions were shown to produce significant changes in the nearest neighbor environment of only one of two inequivalent Cs sites. In Cs3Sb2I9 , the tensors remain axisymmetric below the transition at 85 K, in line with the assumption relying on powder x-ray diffraction data that, below the transition temperature, Cs3Sb2I9has a trigonal structure. The observed temperature variation in the shape of the 133Cs NMR and 127I NQR signals suggests that Cs3Bi2I9may undergo a transition to an incommensurate phase.
27 citations
TL;DR: In this paper, the SO(5) theory was used to explain the superconductivity and antiferromagnetism coexistence in nearly homogeneous and slightly Ge-substituted CeCu2Si2.
Abstract: We report, on the basis of Cu nuclear quadrupole resonance measurements, that superconductivity (SC) and antiferromagnetism (AF) coexist on a microscopic level in CeCu2(Si1-xGex)2, once a tiny amount of 1% Ge (x = 0.01) is substituted for Si. This coexistence arises because Ge substitution expands the unit-cell volume in nearly homogeneous CeCu2Si2 where the SC coexists with slowly fluctuating magnetic waves. We propose that the underlying exotic phases of SC and AF in nearly homogeneous and in slightly Ge-substituted CeCu2Si2 can be accounted for on the basis of the SO(5) theory that unifies the SC and AF. We suggest that the SC and AF in CeCu2Si2 have a common mechanism.
21 citations
21 citations
TL;DR: In this paper, a theoretical treatment of the 2D exchange NQR pulse sequence is presented and applied to the quantitative study of exchange processes in molecular crystals, taking into account the off-resonance irradiation, which critically influences the spin dynamics.
Abstract: A theoretical treatment of the 2D exchange NQR pulse sequence is presented and applied to the quantitative study of exchange processes in molecular crystals. It takes into account the off-resonance irradiation, which critically influences the spin dynamics. The response of a system of spins I = 3/2 in zero applied field, experiencing electric quadrupole couplings, to the three-pulse sequence is analysed. All the tools and mathematical expressions to predict the time evolution of the signal created by a pure NQR multipulse sequence are presented explicitly. The mixing dynamics by exchange and the expected cross-peak intensities as a function of the frequency offset have been derived. The theory is illustrated by a study of the optimization procedure, which is of crucial importance for the detection of the cross- and diagonalpeaks in a 2D exchange spectrum. The systems investigated here were hexachloroethane and tetrachloroethylene, which show threefold and twofold reorientational jumps about the carbon-car...
19 citations
Patent•
05 Nov 2001
TL;DR: In this article, the authors described a method for testing a sample containing quadrupolar nuclei exhibiting a given value of spin-lattice relaxation time, T 1, and disclosed the methods of and apparatus for nuclear quadrupole resonance testing.
Abstract: Methods of and apparatus for Nuclear Quadrupole Resonance (NQR) testing a sample containing quadrupolar nuclei exhibiting a given value of spin-lattice relaxation time, T 1 , are disclosed. The method comprises applying two excitation blocks to excite nuclear quadrupole resonance, there being a given delay time between the two blocks, detecting resonance response signals, and comparing the response signals from respective blocks. The delay time is less than the T 1 value of the nuclei.
19 citations
TL;DR: The results of the 209 Bi NQR experiments carried out on α-Bi 2 O 3, Bi 3 O 4 Br, Bi 2 M 4 O 9 (M =Al, Ga), Bi 2 Ge 3 O 9, and Bi 4 Ge O 12 (Ge 3 O 12) single crystal in external magnetic fields below 500 Oe, applied at various orientations with respect to the crystal axes were observed in applied fields and modeled.
17 citations
TL;DR: In this article, the rotational angle between the epitaxially grown twins is calculated from the strain tensors of the three orientation states, applying an algebraic approach, and the theoretical value Θ = 3.5° is in very good correspondence with the experimental result from the 35Cl NMR studies (~4°).
Abstract: Quadrupolar perturbed 35Cl NMR and 35Cl NQR investigations are performed on single crystals of tetramethylammonium cadmium chloride, (CH3)4NCdCl3 (TMCC), in order to study the formation of ferroelastic domains in the ferroelastic phase II below 118 K in which the hexagonal symmetry of the high temperature phase I is lost. The experimental results cannot simply be explained in terms of the well known monoclinic domain structure but additionally a twin domain structure is found to exist in phase II: six orientational domains are verified from the NMR rotational pattern at 113 K in contrast to the expected number of three for a classical 6/mF2/m transition. The rotational angle Θ between the epitaxially grown twins is calculated from the strain tensors of the three orientation states, applying an algebraic approach. The theoretical value Θ = 3.5° is in very good correspondence with the experimental result from the 35Cl NMR studies (~4°). Similar results were also derived in recent x-ray studies in phase II. In the low temperature phase III below 104 K the number of non-equivalent Cl positions is consistent with both the space group of phase III and the sixfold enlarged size of the unit cell in phase III with respect to that in phase I as observed in XRD studies.
TL;DR: In this paper, the difference in the lightly doped impurity effects on the local magnetic correlation between magnetic Ni and nonmagnetic Zn impurities has been studied by the planar 63 Cu nuclear spin-lattice re...
Abstract: The difference in the lightly doped impurity effects on the local magnetic correlation between magnetic Ni and nonmagnetic Zn impurities has been studied by the planar 63 Cu nuclear spin-lattice re...
TL;DR: In this article, the authors studied low-frequency spin dynamics near the impurity-induced superconductor-to-insulator transition for underdoped high-T c superconductuctor YBa 2 (Cu 1- x M x ) 4 O 8 (M=Ni, Zn) using the Cu nuclear quadrupole resonance (NQR) spin-echo technique.
Abstract: We studied low-frequency spin dynamics near the impurity-induced superconductor-to-insulator transition for underdoped high- T c superconductor YBa 2 (Cu 1- x M x ) 4 O 8 (M=Ni, Zn) using the Cu nuclear quadrupole resonance (NQR) spin-echo technique. We observed remarkable suppression of the normal-state pseudo spin-gap and a loss of Cu NQR spectrum intensity at low temperatures around the critical impurity concentration.
TL;DR: In this paper, the electronic structure of the dimeric compounds, M 2 X 6 (M=Al, Ga, In, I; X=F, Cl, Br, I) and M 2 x 10 (M =Sb, Nb, X=Cl, I, I), is analyzed on the basis of the density functional theory.
Abstract: Analysis of the electronic structure of the dimeric compounds, M 2 X 6 (M=Al, Ga, In, I; X=F, Cl, Br, I) and M 2 X 10 (M=Sb, Nb; X=Cl, Br, I), is carried out on the basis of the density functional theory. The experimental values of the nuclear quadrupole resonance (NQR) parameters such as the quadrupole coupling constant and asymmetry parameter are compared with their calculated values. The binding of the bridge and terminal halogen atoms is analysed in the approach of the natural bond orbital, which permitted conclusions on the nature of the metal–halogen bond. The inversion of the NQR halogen frequencies in the dimers of non-transition and transition elements is explained.
TL;DR: In this article, a linear correlation between the quadrupole coupling constants C (Cu) measured by the 63 Cu NQR/NMR technique on the one hand and C (Zn), measured by 67 Cu/ 67 Zn emission Mossbauer spectroscopy on the other hand has been found.
Abstract: A linear correlation between the quadrupole coupling constants C (Cu) measured by the 63 Cu NQR/NMR technique on the one hand and C (Zn) measured by the 67 Cu/ 67 Zn emission Mossbauer spectroscopy on the other hand has been found. The deviation from the linear dependence for a particular substance indicates a considerable difference of the copper charge state from 2+ or different orientations of the z-axes for the total and lattice electric field gradient (EFG) tensors on 63 Cu. A similar deviation from the linear dependence of C (Cu) on the principal component of the lattice EFG tensor calculated for the copper sites permits to find a difference of the accepted model from the actual charge distribution in the HTSC lattice sites.
TL;DR: In this paper, the authors measured the Cu-NQR spectra in a wide temperature range from 300 K to 1.5 K to investigate the ordering process and the structure of the static spin-charge stripe order in La 2-x - y Eu y Sr...
Abstract: The Cu-NQR spectra were measured in a wide temperature range from 300 K to 1.5 K to investigate the ordering process and the structure of the static spin-charge stripe order in La 2- x - y Eu y Sr ...
TL;DR: In this article, the authors investigated if the NQR signal of La 2-x Sr x CuO 4 in the region x ∼ 1/8 at low temperatures, can also be observed in YBa 2 Cu 3 O y system, and found no evidence in the 60 K plateau and higher carrier concentration regions of y.
Abstract: We have investigated if the wipeout phenomenon observed for the NQR signal of La 2- x Sr x CuO 4 in the region x ∼1/8 at low temperatures, can also be observed in YBa 2 Cu 3 O y system, and found no evidence in the 60 K plateau and higher carrier concentration regions of y . Only in the region of y <6.5, where at least part of hole carriers is localized, the reduction of Cu NQR spectra at low temperatures has been found. The inhomogeneous distribution of these localized carriers seems to cause the wipeout phenomenon. The wipeout phenomenon observed for YBa 2 (Cu 0.98 Zn 0.02 ) 3 O y in the wide region of y can also be understood by the same mechanism.
TL;DR: In this paper, the authors presented the planar 63 Cu nuclear spin-lattice relaxation study of impurity-doped YBa2(Cu1−xMx)4O8 (M=Ni, Zn) at T=4.2-300 K with Cu nuclear quadrupole resonance (NQR) spin-echo technique.
Abstract: We present the planar 63 Cu nuclear spin–lattice relaxation study of impurity-doped YBa2(Cu1−xMx)4O8 (M=Ni, Zn) at T=4.2–300 K with Cu nuclear quadrupole resonance (NQR) spin-echo technique. In the light of an impurity-induced NQR relaxation theory, we estimated the host Cu nuclear spin–lattice relaxation time (T1)HOST, the impurity-induced Cu nuclear spin–lattice relaxation time (τ1), and the wipeout region around the impurity in the superconducting state. The pseudo spin-gap behavior of the host Cu antiferromagnetic spin fluctuation above Tc is not readily removed by a small amount of the impurity. The Zn-induced non-Korringa behavior of (T1)HOST below Tc is in sharp contrast to the doping effect of the magnetic impurity Ni.
TL;DR: In this article, phase transitions and incommensurability in K2SbF5 have been studied by means of 123Sb NQR spectra and spin-lattice relaxation measurements.
Abstract: Phase transitions and incommensurability in K2SbF5 has been studied by means of 123Sb NQR spectra and spin-lattice relaxation measurements. The phase transitions have been obtained at 117, 135 and 260 K. Line shape and temperature dependence of the spin-lattice relaxation time T1 in the temperature range from 135 to 260 K are characteristic for the incommensurate state with the plane wave modulation regime. At 117 to 135 K, a distinct fine structure of NQR spectra has been observed. Redistribution of line intensities with the variation of temperature allows us to suggest that this phase exhibits domain structure, and that one of the domains becomes energetically beneficial on cooling and transforms into the low temperature phase at 117 K. The 123Sb NQR measurements in K2SbF5 show unusually short values of T1, which become close to the spin-spin relaxation time T2 with increasing temperature.
TL;DR: In this article, the authors carried out 27Al and 59Co NMR and nuclear quadrupole resonance (NQR) measurements on UCoAl, which exhibits a meta-magnetic transition in a small magnetic field (H∼1 T) at around 16 K.
TL;DR: It is shown that both the anomalously huge resonance-frequency dependence of the (35)Cl nuclear quadrupole resonance (NQR) spin-lattice relaxation time in BCPS and its anomalous temperature dependence can be explained by large- scale fluctuations of the pinned modulation wave instead of small-scale fluctuations (phasons and amplitudons).
Abstract: We show that both the anomalously huge resonance-frequency dependence of the 3 5 Cl nuclear quadrupole resonance (NQR) spin-lattice relaxation time in BCPS, reported here for the first time, and its anomalous temperature dependence can be explained by large-scale fluctuations of the pinned modulation wave instead of small-scale fluctuations (phasons and amplitudons). The results were obtained by measuring the laboratory (T 1 Q ) and rotating frame (T 1 Q , [ ) 3 5 Cl relaxation times. This is the first time that an effective resonance frequency dependence of the spin-lattice relaxation rate was measured in pure NQR.
TL;DR: The nuclear magnetic dipole moment mu and electric quadrupole moment Q of the beta-emitting 16N(Ipi = 2(-), T(1/2) = 713 s) nucleus have been determined for the first time by detecting its beta-NMR in a MgO crystal and nuclear NQR in a TiO (2) crystal.
Abstract: The nuclear magnetic dipole moment mu and electric quadrupole moment Q of the beta-emitting 16N(Ipi = 2(-), T(1/2) = 713 s) nucleus have been determined for the first time by detecting its beta-NMR in a MgO crystal and beta-NQR (nuclear quadrupole resonance) in a TiO (2) crystal to be /mu/ = (19859+/-00011) mu(N) and /Q/ = (179+/-17) mb, respectively Although the prediction of mu given by the Hartree-Fock calculation agrees well with the experiment, an abnormally small effective charge for neutrons is required to account for the experimental Q
TL;DR: In this article, the asymmetry parameters of electric field gradient tensors on 35Cl nuclei were determined with nutation 35Cl-NQR spectroscopy in zero magnetic field.
Abstract: 35Cl-NQR frequencies of 1,3,5-trichloro-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione and 1,3-dichloro-5,5-dimethylhydantoin were measured at 77 K The asymmetry parameters of electric field gradient (EFG) tensors on 35Cl nuclei were also determined with nutation 35Cl-NQR spectroscopy in zero magnetic field The calculated quadrupole coupling constants and asymmetry parameters for 14N and 35Cl nuclei were compared with the corresponding experimental values for several compounds containing N—Cl bonds The electronic structure of the N—Cl bond in these compounds is discussed in terms of the terminology of lone pairs, hybrid orbitals and NAO charges Copyright © 2001 John Wiley & Sons, Ltd
TL;DR: In this paper, an optimal law of the distribution of the turns of a helical coil is proposed for improving the uniformity of the RF field generated by a surface helical coils with nonlinearly distributed turns.
Abstract: A simple and rather efficient method is proposed for improving the uniformity of the RF field generated by a surface helical coil with nonlinearly distributed turns. An optimal law of the distribution of the turns of a helical coil is suggested. The results of a computer simulation of the field produced by this coil are presented and compared with the data for a conventionally used coil in the form of a linear spiral. The coils were tested during detection of nuclear quadrupole resonance signals on 14N nuclei in a (CH2)6N4polycrystal and demonstrated the efficiency of the technique proposed for improving the field uniformity.
TL;DR: In this paper, the authors measured the Cl Nuclear Quadrupole Resonance (NQR) frequency and spin lattice relaxation time (T1) in the three anisoles 2,3,4,trichloroanisole, 2, 3,6-trichloornisole and 3,5-dichloranisole as a function of pressure up to 5.1 kbar at 300 K.
Abstract: The Cl Nuclear Quadrupole Resonance (NQR) frequency ( Q) and spin lattice relaxation time (T1) in the three anisoles 2,3,4-trichloroanisole, 2,3,6-trichloroanisole and 3,5-dichloroanisole have been measured as a function of pressure upto 5.1 kbar at 300 K, and the data have been analysed to estimate the temperature coefficients of the NQR frequency at constant volume. All the three compounds show a non linear variation of the NQR frequency with pressure, the rate of which is positive and decreases with increasing pressure. In case of 3,5-dichloroanisole the value becomes negative in the higher range of pressure studied. The spin lattice relaxation time T1 in all the three compounds shows a weak dependence on pressure, indicating that the relaxation is mainly due to the torsional motions.
TL;DR: In this paper, the magnetic properties of bismuth-III oxide-based Main Group element compounds were studied using single-crystal 209Bi NQR in external magnetic fields.
Abstract: It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that α-Bi2O3, Bi3O4Br and mixed oxides Bi2O3· 2Al2O3, Bi2O3· 2Ga2O3, Bi2O3· 3GeO2, and 2Bi2O3· 3GeO2exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3were prepared and studied using 209Bi NQR. The quadrupole interactions of the 209Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the 209Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal 209Bi NQR in external magnetic fields.
TL;DR: In this paper, a drastic temperature dependence of the NQR spectrum near T N, in which a single 69 Ga NMR line of 19.8 MHz in the paramagnetic state rapidly vanishes at 70 K and a double peak appears at 17.2 and 16.55 MHz between 63 and 70 K.
TL;DR: The double resonance imaging method offers the advantages of higher spatial resolution and straightforward image reconstruction for powder samples compared with rotating-frame and Zeeman-perturbated nuclear quadrupole resonance encoding techniques.
TL;DR: In this article, the authors investigated the possible static spin-charge stripe order and obtained an insight for a glassy nature of the ordering process, showing that the charge order is triggered at T charge ≈70 K. But the spin order is still quasi static in NQR time scale until T spin (T spin ), the characteristic broad spectrum reappears.
Abstract: Cu-NQR spectra in La 2− x − y Sr x Y y CuO 4 ( x =1/8, y =0.04) were measured to investigate the possible static spin–charge stripe order. We obtained an insight for a glassy nature of the ordering process. The charge order is triggered at T charge ≈70 K. But the spin order is still quasi static in NQR time scale until T spin ( T spin ), the characteristic broad spectrum reappears. The broad spectrum is simulated satisfactorily based upon the stripe model with the modulation amplitude of the Cu moment of about 0.22 μ B .
TL;DR: In this paper, a review of NMR and nuclear quadrupole resonance (NQR) experiments performed in La 2 CuO 4, YBa 2 Cu 3 O 6, and Ca(Sr)CuO 2 which are the antiferromagnetic parent compounds of some high-temperature superconductors are considered.