Showing papers on "Nuclear quadrupole resonance published in 2013"

Nitrogen-14 Nuclear Quadrupole Resonance Spectroscopy: A Promising Analytical Methodology for Medicines Authentication and Counterfeit Antimalarial Analysis

Abstract: We report the detection and analysis of a suspected counterfeit sample of the antimalarial medicine Metakelfin through developing nitrogen-14 nuclear quadrupole resonance ((14)N NQR) spectroscopy at a quantitative level. The sensitivity of quadrupolar parameters to the solid-state chemical environment of the molecule enables development of a technique capable of discrimination between the same pharmaceutical preparations made by different manufacturers. The (14)N NQR signal returned by a tablet (or tablets) from a Metakelfin batch suspected to be counterfeit was compared with that acquired from a tablet(s) from a known-to-be-genuine batch from the same named manufacturer. Metakelfin contains two active pharmaceutical ingredients, sulfalene and pyrimethamine, and NQR analysis revealed spectral differences for the sulfalene component indicative of differences in the processing history of the two batches. Furthermore, the NQR analysis provided quantitative information that the suspected counterfeit tablets contained only 43 ± 3%, as much sulfalene as the genuine Metakelfin tablets. Conversely, conventional nondestructive analysis by Fourier transform (FT)-Raman and FT-near infrared (NIR) spectroscopies only achieved differentiation between batches but no ascription. High performance liquid chromatography (HPLC)-UV analysis of the suspect tablets revealed a sulfalene content of 42 ± 2% of the labeled claim. The degree of agreement shows the promise of NQR as a means of the nondestructive identification and content-indicating first-stage analysis of counterfeit pharmaceuticals.

NMR and NQR Studies on Non-centrosymmetric Superconductors Re7B3, LaBiPt, and BiPd

Abstract: We report the nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements for non-centrosymmetric superconductors Re7B3, LaBiPt, and BiPd containing heavy elements. For all three compounds, the spin–lattice relaxation rate \(1/T_{1}\) shows a coherence peak just below \(T_{\text{c}}\) and decreases exponentially at low temperatures, which indicates that an isotropic superconducting gap is dominant in these compounds. In BiPd, the height of the coherence peak just below \(T_{\text{c}}\) is much suppressed, which suggests that there exists a substantial component of gap with nodes in this compound. Our results indicate that heavy element is not the only factor, but the extent of inversion symmetry breaking is also important to induce a large spin–orbit coupling and an unconventional superconducting state.

A study of transition-metal organometallic complexes combining 35Cl solid-state NMR spectroscopy and 35Cl NQR spectroscopy and first-principles DFT calculations.

Abstract: A series of transition-metal organometallic complexes with commonly occurring metal-chlorine bonding motifs were characterized using (35)Cl solid-state NMR (SSNMR) spectroscopy, (35)Cl nuclear quadrupole resonance (NQR) spectroscopy, and first-principles density functional theory (DFT) calculations of NMR interaction tensors. Static (35)Cl ultra-wideline NMR spectra were acquired in a piecewise manner at standard (9.4 T) and high (21.1 T) magnetic field strengths using the WURST-QCPMG pulse sequence. The (35)Cl electric field gradient (EFG) and chemical shielding (CS) tensor parameters were readily extracted from analytical simulations of the spectra; in particular, the quadrupolar parameters are shown to be very sensitive to structural differences, and can easily differentiate between chlorine atoms in bridging and terminal bonding environments. (35)Cl NQR spectra were acquired for many of the complexes, which aided in resolving structurally similar, yet crystallographically distinct and magnetically inequivalent chlorine sites, and with the interpretation and assignment of (35)Cl SSNMR spectra. (35)Cl EFG tensors obtained from first-principles DFT calculations are consistently in good agreement with experiment, highlighting the importance of using a combined approach of theoretical and experimental methods for structural characterization. Finally, a preliminary example of a (35)Cl SSNMR spectrum of a transition-metal species (TiCl4) diluted and supported on non-porous silica is presented. The combination of (35)Cl SSNMR and (35)Cl NQR spectroscopy and DFT calculations is shown to be a promising and simple methodology for the characterization of all manner of chlorine-containing transition-metal complexes, in pure, impure bulk and supported forms.

Tautomerism and Possible Polymorphism in Solid Hydroxypyridines and Pyridones Studied by 14N NQR

Abstract: 14N nuclear quadrupole resonance frequencies have been measured in solid 2-pyridone, 3-hydroxypyridine, and 4-pyridone by 1H–14N nuclear quadrupole double resonance. Two slightly nonequivalent nitr...

Valence Crossover of Ce Ions in CeCu2Si2 under High Pressure - Pressure Dependence of the Unit Cell Volume and the NQR Frequency

Abstract: The pressure dependence of the valence of Ce ions in CeCu2Si2 has been investigated by means of X-ray powder diffraction (XRPD) and nuclear quadrupole resonance (NQR) measurements. The high-pressure XRPD measurements were carried out at 12 K for CeCu2Si2 and CeCu2Ge2. Precise measurements under smoothly-applied pressure were achieved through the selection of the gasket material of a diamond anvil cell. The jump of the unit cell volume, which was reported previously in CeCu2Ge2, was not observed within the experimental accuracy, indicating the absence of a first-order valance transition. The pressure dependence of 63Cu-NQR frequency νQ measured in CeCu2Si2 was compared with that calculated from the measured lattice parameters. The νQ's were calculated for the two cases of LaCu2Si2 and CeCu2Si2, corresponding to localized and itinerant cases for \(4f\) electrons, respectively. The measured and calculated slopes dνQ/dP show good agreement. A small but significant deviation from the pressure-linear dependence...

The Influence of Pressure in Paracetamol Tablet Compaction on 14N Nuclear Quadrupole Resonance Signal

Abstract: 14N nuclear quadrupole resonance (14N NQR) of several commercially available paracetamol tablets was measured. The spectra of two polymorphs are presented. The linewidths of the correspondent 14N NQR lines in all the measured samples containing the room-temperature stable monoclinic polymorph were noticeably different. We proved experimentally that the linewidth differences are the consequence of different compacting pressure in the production of tablets.

Method and system for applying nqr pulse sequences

Abstract: A method and system for applying nuclear quadrupole resonance (NQR) sequences to a substance and determining presence of a chemical species within the substance using the sequences are described herein. The method includes applying an NQR pulse sequence to the substance using a non-resonant transmitter circuit. The method further includes detecting a NQR signal within the substance and determining presence of a chemical species within the substance using the NQR signal.

Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB6

Abstract: We report high-pressure studies of X-ray diffraction and 11 B-nuclear magnetic resonance (NMR) in the intermediate- valence compound SmB6. The pressure dependence of the lattice constant was precisely determined and no anomaly was observed up to 9.1 GPa. The temperature dependence of the nuclear quadrupole resonance frequencyQ, obtained from the 11 B-NMR measurements, is predominantly contributed by on-site charge distribution. Using the relationship betweenQ and Sm valence at ambient pressure reported previously, we estimate the pressure dependence of the Sm valence up to 6 GPa as well. The increase in the Sm valence accelerates with pressure and reaches an increase of about 10% at 6 GPa. The pressure-induced localization of Sm 4f -holes may be responsible for the long-range magnetic order under pressure.

Low-power stimulated emission nuclear quadrupole resonance detection system utilizing Rabi transitions

Abstract: The application of CW radar techniques to Nuclear Quadrupole Resonance (NQR) detection of nitrogen based explosives and chlorine based narcotics enables the use of low power levels, in the range of 10’s of watts, to yield high signal strengths. By utilizing Rabi transitions the nucleus oscillates between states one and two under the time dependent incident electromagnetic field and alternately absorbs energy from the incident field while emitting coherent energy via stimulated emission. Through the application of a cancellation algorithm the incident field is eliminated from the NQR response, allowing the receive signal to be measured while transmitting. The response signal is processed using matched filters of the NQR response which enables the direct detection of explosives. This technology has applicability to the direct detection of explosives and narcotics for security screening, all at safe low power levels, opposed to the current XRay and Millimeter wave screening systems that detect objects that may contain explosives and utilize high power. The quantum mechanics theoretical basis for the approach and an application for a system for security screening are described with empirical results presented to show the effects observed.

Carbon Doping of Defect Sites in Stone–Wales Defective Boron-nitride Nanotubes: A Density Functional Theory Study

Abstract: We have performed a density functional theory study to investigate the effect of carbon doping on Stone–Wales (SW) defective sites in the armchair (4, 4), (5, 5) and (6, 6) BNNTs, in order to remove structural instability induced by homonuclear N–N and B–B bonds. Two different orientations of SW defect are considered, parallel and diagonal, and then C atoms are doped at different positions of the defect sites. In general, it seems that among the considered arrangements, C atoms prefer to be substituted for the homonuclear B–B bond. The larger HOMO–LUMO band gaps for the most stable configurations indicate that C doping at B–B sites is kinetically more favorable than the other ones. According to calculated nuclear quadrupole resonance (NQR) parameters as a result of C-doping on SW defective sites, the quadrupole coupling constants (C Q ) of boron nuclei at defective sites decrease by about 0.508–1.406 MHz while 14N C Q of the defective sites, except for N8, increases. Interestingly, C Q of the N sites directly connected to dopant sites has maximum increment (0.612–2.596 MHz) while C Q of the N sites belonging to the B2N3 pentagon is undergone to some minor changes.

Hydrogen Bonds in Cocrystals and Salts of 2-Amino-4,6-dimethylpyrimidine and Carboxylic Acids Studied by Nuclear Quadrupole Resonance

Abstract: 14N and 17O nuclear quadrupole resonance frequencies have been measured in 1:1 cocrystals and salts of 2-amino-4,6-dimethylpyrimidine and several carboxylic acids. A systematic decrease of the 17O quadrupole coupling constant on increasing strength of the hydrogen bond is observed in cocrystals bound by O–H···N hydrogen bonds. The O–H distances deduced from the line widths of the 17O NQR lines show that the hydrogen atom is in a hydrogen bond formed by a carboxylic groups for about 0.01 nm displaced from the oxygen atom toward the center of the hydrogen bond. In the O–H···N hydrogen bond formed by the hydroxyl group, which is only slightly longer than the hydrogen bonds formed by the carboxyl group, the hydrogen atom is much less displaced. A linear relation between the 14N quadrupole coupling constant and the sum of the inverse third powers of the H···A (A = O or N) distances is deduced for the amino group. A linear correlation of the principal values of the 14N quadrupole coupling tensor in −NH2, as obs...

NQR/NMR and Mössbauer spectroscopy of sulfides: potential and versatility

Abstract: Nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and nuclear gamma-resonance (NGR or Mossbauer Effect) methods are generally described as highly sensitive tools in studies of local electronic structure and symmetry in solid-state materials. This is due to high informativity in electronic structure investigations, high resolution in phase-structural diagnostics (down to nano-scale), possibility to study polycrystalline and complex compounds, and to the non-destructive character of these methods. As applied to Earth sciences, both NQR/NMR and Mossbauer spectroscopy methods contribute to mineralogical material science and mineral physics. Another important aspect is the fact that these methods, as demonstrated recently, belong to unique techniques suitable for on-line bulk mineralogical analysis. This includes remotely operated sensors used with conveyor systems in mining/materials handling and similar applications where real-time data collection/processing provides significant commercial benefits. These developments open new pathways for NQR/NMR and Mossbauer spectroscopy applications. Notably, NQR/NMR and Mossbauer effects are observed primarily on different nuclei-probes but provide similar information about the local properties of materials (hyperfine fields, electric field gradients and relaxation effects). This makes NQR/NMR and Mossbauer methods mutually complementary despite their significant technical differences. This paper includes examples of recent applications of NQR, NMR and Mossbauer spectroscopic tools to studies of copper-, antimony- and iron-containing sulfides, demonstrating how these methods can contribute to an improved understanding of geochemical problems.

Evolution of magnetic and crystal structures in the multiferroic FeTe2O5Br

Abstract: Neutron diffraction and nuclear quadrupole resonance (NQR) measurements were employed to investigate magnetic order in the nonferroelectric phase preceding the low-temperature multiferroic state in FeTe2O5Br. Refinement of the neutron diffraction data and simulations of Br-79,Br-81 NQR spectra reveal that the incommensurate magnetic ordering in the nonferroelectric state comprises amplitude-modulated magnetic moments, similar to that seen in the multiferroic state. The two ordered states differ in the orientation of the magnetic moments and phase shifts between modulation waves. Surprisingly, all symmetry restrictions for the electric polarization are absent in both states. The different ferroelectric responses of the two states are thus argued to arise from the differences in the phase shifts between certain modulation waves, which cancel out in the nonferrolectric state. DOI: 10.1103/PhysRevB.87.144408

Nuclear Quadrupole Resonance Study of Hydrogen Bonds in Solid 2-Methylbenzimidazole and 5,6-Dimethylbenzimidazole

Abstract: Substituted imidazole and benzimidazole often form polar hydrogen-bonded chains in the solid state. 2-Methylbenzimidazole is known to be a high-temperature organic ferroelectric. We have measured t...

Inhomogeneous magnetism in the doped kagome lattice of LaCuO2.66

Abstract: The hole-doped kagome lattice of Cu${}^{2+}$ ions in LaCuO${}_{2.66}$ was investigated by nuclear quadrupole resonance, electron spin resonance, electrical resistivity, bulk magnetization, and specific-heat measurements. For temperatures above $\ensuremath{\sim}180$ K, the spin and charge properties show an activated behavior suggestive of a narrow-gap semiconductor. At lower temperatures, the results indicate an insulating ground state which may or may not be charge ordered. While the frustrated spins in remaining patches of the original kagome lattice might not be directly detected here, the observation of coexisting nonmagnetic sites, free spins, and frozen moments reveals an intrinsically inhomogeneous magnetism. Numerical simulations of a $\frac{1}{3}$-diluted kagome lattice rationalize this magnetic state in terms of a heterogeneous distribution of cluster sizes and morphologies near the site-percolation threshold.

Microscopic Properties of the Heavy-Fermion Superconductor PuCoIn$_5$ Explored by Nuclear Quadrupole Resonance

Abstract: We report $^{115}$In nuclear quadrupolar resonance (NQR) measurements on the heavy-fermion superconductor PuCoIn$_5$, in the temperature range $0.29{\rm K}\leq T\leq 75{\rm K}$. The NQR parameters for the two crystallographically inequivalent In sites are determined, and their temperature dependence is investigated. A linear shift of the quadrupolar frequency with lowering temperature below the critical value $T_c$ is revealed, in agreement with the prediction for composite pairing. The nuclear spin-lattice relaxation rate $T_1^{-1}(T)$ clearly signals a superconducting (SC) phase transition at $T_c\simeq 2.3$K, with strong spin fluctuations, mostly in-plane, dominating the relaxation process in the normal state near to $T_c$. Analysis of the $T_1^{-1}$ data in the SC state suggests that PuCoIn$_5$ is a strong-coupling $d$-wave superconductor.

Study of the EFG tensor at 75As nuclei in Ge-As-Se chalcogenide glasses.

Abstract: Asymmetry parameters of the electric field gradient tensor at 75As nuclei were determined for chalcogenide glassy semiconductors (CGS) of the Ge-As-Se system by comparing the experimental and simulated 75As nuclear quadrupole resonance nutation interferograms. The electric field gradient asymmetry in CGS was analyzed, and it is believed that a structural change in these glassy semiconductors takes place at = 2.425. Electron paramagnetic resonance spectra of the Ge-As-Se system were obtained for the first time. A comparison was made between the results of analysis of the Ge-As-Se system by nuclear quadrupole resonance and electron paramagnetic resonance methods, and this allowed us to make the supposition that a structural phase transition occurs at = 2.4 from two-dimensional to three-dimensional CGS structure. Copyright © 2013 John Wiley & Sons, Ltd.

A DFT Computation for Comparison of NQR of O 2 , N 2 and CO over the Surface of Single-Walled Carbon Nanotubes

Abstract: In this study we assumed Single-Walled Carbon Nano Tubes (SWCNTs) as ideal candidates for various applications of gas sensors due to their amazing physical adsorption properties. The adsorption behavior of selected nitrogen, oxygen and CO molecules on the surface of the Single-Walled Carbon Nano Tubes (SWCNTs) was studied by the Density Functional Theory (DFT) (B3LYP/6-311G*) using the Gaussian 98 software. We studied the Nuclear Quadrupole Resonance (NQR) of the armchair (4, 4) SWCNTs with the optimal diameter of 5.6 A and the length of 9.8 A. For the first time, DFT calculations were performed to calculate oxygen and nitrogen the interaction of quadrupole moment with Electric Field Gradient (EFG) in NQR in the representative considered model of the (N2-CNTs), (O2-CNTs) and (CO-CNTs). The evaluated NQR parameters reveal that the EFG tensors of Oxygen-17, Nitrogen-14 and Carbon-13 are influenced and show particular trends from gas molecules in the SWCNTs due to the contribution of N-N, O-O and C-O gas molecules of SWCNTs.

35Cl NQR frequency and spin lattice relaxation time in 3,4-dichlorophenol as a function of pressure and temperature.

Abstract: The pressure dependences of 35Cl nuclear quadrupole resonance (NQR) frequency, temperature and pressure variation of spin lattice relaxation time (T1) were investigated in 3,4-dichlorophenol T1 was measured in the temperature range 77–300 K Furthermore, the NQR frequency and T1 for these compounds were measured as a function of pressure up to 5 kbar at 300 K The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities W1 and W2 for the Δm = ±1 and Δm = ±2 transitions were also obtained A nonlinear variation of NQR frequency with pressure has been observed and the pressure coefficients were observed to be positive A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency An attempt is made to compare the torsional frequencies evaluated from NQR data with those obtained by IR spectra On selecting the appropriate mode from IR spectra, a good agreement with torsional frequency obtained from NQR data is observed The previously mentioned approach is a good illustration of the supplementary nature of the data from IR studies, in relation to NQR studies of compounds in solid state Copyright © 2012 John Wiley & Sons, Ltd

Low power stimulated emission nuclear quadrupole resonance detection at multiple reference power levels

Abstract: System and methods for detecting substances such as explosives via the nuclear quadrupole resonance effect. We observe that the nuclear quadrupole resonances of explosives located within a cavity portal involve continuous Rabi transitions which are nonlinear processes since stimulated emission occurs. In other words, where there are no resonances caused by the presence of an explosive, high average power and low average power measurements should be identical. However, when resonances are stimulated by the system, the difference between these two conditions can be compared to determine a correction to measurements made when a person located in the cavity has explosive material on their person, without the need for separate empty portal or elaborate calibration procedures.

Heavy Fermion Superconductor Ce2PdIn8 studied by 115In Nuclear Quadrupole Resonance

Abstract: We have performed nuclear quadrupole resonance (NQR) measurements on a recently-discovered heavy-fermion superconductor Ce2PdIn8 with superconducting critical temperature Tc = 0.64 K. Below coherent temperature Tcoh ~ 30 K, the spin-lattice relaxation rate 1/T1 decreases with decreasing temperature T and is proportional to T1/2 between Tc and Tcoh. This is clearly different from the Fermi-liquid behavior in which the T dependence is proportional to T, and indicates that Ce2PdIn8 is located on the verge of antiferromagnetic quantum critical point from the view point of the NQR. Below Tc, 1/T1 shows no coherence peak and is proportional to T3. This is clear evidence for the realization of unconventional superconductivity with line nodes in this compound.

Sb NQR study of the filled skutterudite CeFe4Sb12 synthesized under high pressure

Abstract: We report the results of Sb nuclear quadrupole resonance (NQR) measurements on the filled skutterudite CeFe4Sb12 synthesized under high pressure (HP) and compare them with those for the sample synthesized under ambient pressure (AP) to understand the influence of the Ce-site filling fraction. The NQR spectra for the HP sample are much sharper than those for the AP sample, suggesting that the Ce filling fraction is higher. Also, the nuclear spin-lattice relaxation rate 1/T 1 follows an exponential decrease 1/T 1 ∝ exp(−Δ/k B T), with the gap being Δ/k B = 270 K at temperatures above 100 K, which is larger than that for the AP sample. This result suggests that the c-f hybridization is enhanced by increasing the Ce-site filling fraction.

Electronic Structure and Indirect Spin-Spin Interactions in Bournonite (CuPbSbS 3 ) According to Antimony Nuclear Quadrupole Resonance

Abstract: A complex sulfide CuPbSbS3 (bournonite) has been studied by the nuclear quadrupole resonance on 121,123Sb. The temperature dependences of the spectroscopic and relaxation parameters in the temperature range of 10–295 K have been obtained. The crystallochemical features of the environment of the two non-equivalent Sb positions in the unit cell have been revealed from the nuclear quadrupole resonance spectra. The existence of the lattice vibrations with the frequency ω = 110 cm−1 has been demonstrated on the basis of the temperature dependence of the nuclear quadrupole resonance frequencies. Slow beats have been observed on the decay curve of the spin echo signal. Experimental data have been analyzed in order to reveal the existence of the indirect spin-spin interactions involving Sb atoms. The indirect spin-spin coupling constant has been estimated as J = 2.5 ± 0.5 kHz.

Investigation of the multiplicities of nuclear quadrupole resonance spectrums isotopes 113,115In in crystals InSe grown from the melt

Abstract: For researchers, the problem of interpreting the origin nature of NQR spectra multiplicity is always one of the main experimental tasks. For the purpose of interpreting the nature of the occurrence of NQR spectra multiplicity in the layered crystal InSe, the spectra of NQR 113,115 In for four spin transitions, the average values of which are only approximately satisfied the ratio ν1: ν2: ν3: ν4 =1: 2:3:4 were studied. In the studied NQR spectra, two multiplet groups, confirming the presence of polytypic structure in crystals are clearly observed. The feature of multiplet groups is the presence of fine structure with the splitting constant, which is clearly observed for the three higher transitions and constitutes10 ± 0,5 kHz. The quantitative similarity of the spectra 113,115 In in InSe reflects that the corresponding splitting occurs almost entirely due to the interaction of nuclei In. It is established that for higher transitions deviation is observed. It is shown that, in multiplet groups for higher-order transitions, multiplet groups of lines are observed that, in our opinion, is connected with the presence hexadecapole interaction with the electric field gradient of crystal. This interaction is caused not only by p-, but also d-, f- electrons in layered crystal with highly distorted configuration of the charge distribution in the vicinity of indium nuclei. In addition, as a result of exciting the electrons d- or f- of the indium atom shell by coordinating interactions, the additional contribution of hexadepole moment in the form of additional lines in the multiplet spectra of NQR may occur.

Study of Relationship between NQR Signal Amplitudes and Nitrogen Contents in Explosive Simulants

Abstract: This paper investigated the relationship of the nuclear quadrupole resonance (NQR) signal amplitudes with nitrogen contents and frequencies of explosive simulants based on the NQR explosive detection principle. The NQR signals of urea, urotropine and sodium nitrite were detected by experiment at room temperature, and the signal spectra of the nitrogenous compounds with different weights were obtained. The results indicate that the NQR signal amplitudes of the same mimic are increasing linearly with the increase of weights under the same experimental conditions, meanwhile, the higher the frequency, the greater the signal amplitude. The NQR signal amplitudes of different mimics do not rely on the nitrogen contents, but depend on the other internal factors such as relaxation times, NQR frequencies and so on. The experimental data are consistent with the theoretical predictions. The results will be of value to the detection of NQR signals in explosives and the research on how to improve the signal-to-noise ratio (SNR).

63,65Cu Nuclear Resonance Study of the Coupled Spin Dimers and Chains Compound Cu2Fe2Ge4O13

Abstract: Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) of Cu have been measured in a coupled spin dimers and chains compound Cu2Fe2Ge4O13. Cu NQR has also been measured in an isostructural material Cu2Sc2Ge4O13 including only spin dimers. Comparison of the temperature dependence of the 63Cu nuclear spin-lattice relaxation rate between the two compounds reveals that the Fe chains in Cu2Fe2Ge4O13 do not change a spin gap energy of the Cu dimers from that in Cu2Sc2Ge4O13, contributing additionally to the relaxation rate at the Cu site. A modestly large internal field of 3.39 T was observed at the Cu site in the antiferromagnetic state of Cu2Fe2Ge4O13 at 4.2 K, which is partly because of quantum reduction of the ordered moment of a Cu atom. The internal field and the ordered moment of Cu are noncollinear due to large anisotropy of the hyperfine interaction at the Cu site. A model analysis of the internal field based on the fourfold planar coordination of Cu suggests that a 3d hole of the Cu2+ ion is mainly in the d(x2-y2) orbital state.

Dimensionality of Spin Modulations in 1/8-Doped Lanthanum Cuprates from the Perspective of NQR and μSR Experiments

Abstract: We investigate the dimensionality of inhomogeneous spin modulation patterns in the cuprate family of high-temperature superconductors with particular focus on 1/8-doped lanthanum cuprates. We compare one-dimensional stripe modulation pattern with two-dimensional checkerboard of spin vortices in the context of nuclear quadrupole resonance (NQR) and muon spin rotation (μSR) experiments. In addition, we also consider the third pattern, a two-dimensional superposition of spin spirals. Overall, we have found that none of the above patterns leads to a consistent interpretation of the two types of experiments considered. This, in particular, implies that the spin vortex checkerboard cannot be ruled out on the basis of available NQR/μSR experimental results.