Nuclear Magnetic Resonance Linewidth Research Articles

Ultralow-field nuclear magnetic resonance of liquids confined in ferromagnetic and paramagnetic materials

A nuclear magnetic resonance (NMR) procedure is used to measure weak magnetic fields in the vicinity of dilute ferromagnetic and/or paramagnetic materials. By detecting 1H Larmor precession in common solvents at extremely low frequencies (<50 Hz), the magnetic field produced by remanent magnetization of the material is measured by NMR to a precision of <1 nT. In one example, the technique is used to quantify the magnitude and direction of remanent magnetization in a common aluminum alloy. In another example, a 1H NMR linewidth <1 Hz is demonstrated for liquid decane (n-C10H22) embedded inside a mesoporous silica matrix, despite the high concentration of paramagnetic cobalt sites that produce magnetic susceptibility gradients in the system. Application to systems of industrial relevance is discussed.

Electron paramagnetic resonance and 1H nuclear magnetic resonance study of Y-doping effect on the hydrogen shallow donors in ZnO nanoparticles

Hydrogen shallow donors in sol-gel-derived pristine and rare-earth Y-doped ZnO nanoparticles have been investigated by electron paramagnetic resonance (EPR) and high-resolution 1H nuclear magnetic resonance (NMR). It is shown by EPR measurements that the energy level of the hydrogen shallow donors in the Y-doped ZnO is much deeper (E ∼ 174 meV) than in the pristine ZnO (E ∼ 75 meV). The temperature-dependent 1H NMR chemical shift and linewidth measurements of the pristine and the Y-doped ZnO systems indicated that Y-doping effectively modifies the lattice environment and hinders the hydrogen motions in the ZnO nanoparticles.

Site-resolved imaging of beryllium ion crystals in a high-optical-access Penning trap with inbore optomechanics.

We present the design, construction, and characterization of an experimental system capable of supporting a broad class of quantum simulation experiments with hundreds of spin qubits using 9Be+ ions in a Penning trap. This article provides a detailed overview of the core optical and trapping subsystems and their integration. We begin with a description of a dual-trap design separating loading and experimental zones and associated vacuum infrastructure design. The experimental-zone trap electrodes are designed for wide-angle optical access (e.g., for lasers used to engineer spin-motional coupling across large ion crystals) while simultaneously providing a harmonic trapping potential. We describe a near-zero-loss liquid-cryogen-based superconducting magnet, employed in both trapping and establishing a quantization field for ion spin-states and equipped with a dual-stage remote-motor LN2/LHe recondenser. Experimental measurements using a nuclear magnetic resonance (NMR) probe demonstrate part-per-million homogeneity over 7 mm-diameter cylindrical volume, with no discernible effect on the measured NMR linewidth from pulse-tube operation. Next, we describe a custom-engineered inbore optomechanical system which delivers ultraviolet (UV) laser light to the trap and supports multiple aligned optical objectives for topview and sideview imaging in the experimental trap region. We describe design choices including the use of nonmagnetic goniometers and translation stages for precision alignment. Furthermore, the optomechanical system integrates UV-compatible fiber optics which decouple the system's alignment from remote light sources. Using this system, we present site-resolved images of ion crystals and demonstrate the ability to realize both planar and three-dimensional ion arrays via control of rotating wall electrodes and radial laser beams. Looking to future work, we include interferometric vibration measurements demonstrating root-mean-square trap motion of ∼33 nm (∼117 nm) in the axial (transverse) direction; both values can be reduced when operating the magnet in free-running mode. The paper concludes with an outlook toward extensions of the experimental setup, areas for improvement, and future experimental studies.

Using NMR Relaxometry to Probe Yb3+–Er3+ Interactions in Highly Doped Nanocrystalline NaYF4 Nanostructures

Solid-state nuclear magnetic resonance (NMR) spectroscopy is used to study heavily Yb3+ and Er3+ doped, fluorescent NaY1–x–yYbxEryF4 nanoparticles. An understanding of the 19F wide line NMR respons...

Bulk Li mobility enhancement in Spark Plasma Sintered Li(7−3x)AlxLa3Zr2O12 garnet

Li(7−3×)AlxLa3Zr2O12 (LLAZO) Al-doped garnets display high ionic conductivity in the range of ~ 10−4 S.cm−1 at room temperature and are thus envisioned for future solid-state batteries. In this study, LLAZO powders with two doping levels were synthetized using a solid-state route and sintered using Spark Plasma Sintering (SPS). Both pristine and SPS crushed pellet powders were investigated using X-Ray Diffraction (XRD) confirming the formation of the most conducting cubic phase. Ionic conductivity measurements were performed using electrochemical impedance spectroscopy. Li and Al distributions among available sites were identified using Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) experiments, and Li mobility was explored using 7Li static wideline NMR spectroscopy. Results show that SPS treatment, beyond producing highly densified pellets, mainly modifies Al distribution and strongly impacts the bulk Li+ mobility.

Structural phase transition, precursory electronic anomaly, and strong-coupling superconductivity in quasi-skutterudite (Sr1−xCax)3Ir4Sn13 and Ca3Rh4Sn13**Project supported by the National Natural Science Foundation of China (Grant Nos. 11674377 and 11634015), the National Key R&D Program of China (Grant Nos. 2017YFA0302904 and 2016YFA0300502), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020200). J. Y. is supported

The interplay between superconductivity and structural phase transition has attracted enormous interest in recent years. For example, in Fe-pnictide high temperature superconductors, quantum fluctuations in association with structural phase transition have been proposed to lead to many novel physical properties and even the superconductivity itself. Here we report a finding that the quasi-skutterudite superconductors (Sr1−xCax)3Ir4Sn13 (x = 0, 0.5, 1) and Ca3Rh4Sn13 show some unusual properties similar to the Fe-pnictides, through 119Sn nuclear magnetic resonance (NMR) measurements. In (Sr1−xCax)3Ir4Sn13, the NMR linewidth increases below a temperature T* that is higher than the structural phase transition temperature Ts. The spin-lattice relaxation rate (1/T1) divided by temperature (T), 1/T1T and the Knight shift K increase with decreasing T down to T*, but start to decrease below T*, and followed by more distinct changes at Ts. In contrast, none of the anomalies is observed in Ca3Rh4Sn13 that does not undergo a structural phase transition. The precursory phenomenon above the structural phase transition resembles that occurring in Fe-pnictides. In the superconducting state of Ca3Ir4Sn13, 1/T1 decays as exp(−Δ/kBT) with a large gap Δ = 2.21kBTc, yet without a Hebel–Slichter coherence peak, which indicates strong-coupling superconductivity. Our results provide new insight into the relationship between superconductivity and the electronic-structure change associated with structural phase transition.

Thermodynamic properties and NMR study of tetragonal tetrahalogen-metallate dihydrate crystals of Rb2[CuX4]·2H2O (X = Cl− and Br−)

The thermodynamic properties and phase transitions in Rb2[CuBr4]·2H2O are studied through differential scanning calorimetry (DSC), thermogravimetric analysis, and nuclear magnetic resonance (NMR) experiments. The DSC endothermic peaks near 337 and 353 K are accompanied by the partial escape of H2O. The temperature dependence of the NMR resonance frequency, line width, and spin–lattice relaxation time near the transition temperatures are related to variations in the symmetry of the environments of Rb(I) ions. The DSC peaks seem to correspond to a chemical change caused by thermal decomposition, rather than a physical change such as a structural phase transition. The results obtained here are compared to those of Rb2[CuCl4]·2H2O crystal from our previous study.

NMR evidence of charge fluctuations in multiferroic CuBr2**Project supported by the Ministry of Science and Technology of China (Grant No. 2016YFA0300504), the National Natural Science Foundation of China (Grant No. 11374364), the Fundamental Research Funds for the Central Universities of China, and the Research Funds of Renmin University, China (Grant No. 14XNLF08).

We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance (NQR), and zero-field nuclear magnetic resonance (NMR) measurements on single crystals of multiferroics CuBr2. High quality of the sample is demonstrated by the sharp magnetic and magnetic-driven ferroelectric transition at 74 K. The zero-field 79Br and 81Br NMR are resolved below TN. The spin-lattice relaxation rates reveal charge fluctuations when cooled below 60 K. Evidences of an increase of NMR linewidth, a reduction of dielectric constant, and an increase of magnetic susceptibility are also seen at low temperatures. These data suggest an emergent instability which competes with the spiral magnetic ordering and the ferroelectricity. Candidate mechanisms are discussed based on the quasi-one-dimensional nature of the magnetic system.

Antiferromagnetic Mott insulating state in the single-component molecular material Pd(tmdt) 2

A family of compounds built by a single molecular species, $M$(${\mathrm{tmdt})}_{2}$, with a metal ion, $M$, and organic ligands, tmdt, affords diverse electronic phases due to $M$-dependent interplays between $d$ electrons in $M$, and $\ensuremath{\pi}$ electrons in tmdt. We investigated the spin state in $\mathrm{Pd}{(\mathrm{tmdt})}_{2}$, a $\ensuremath{\pi}$-electron system without a $d$-electron contribution, through $^{1}\mathrm{H}$ nuclear magnetic resonance (NMR) and muon-spin resonance experiments. The temperature profiles of the NMR linewidth, relaxation rate, and asymmetry parameter in muon decay show an inhomogeneous antiferromagnetic order with moments distributed around $\ensuremath{\sim}0.1{\ensuremath{\mu}}_{\mathrm{B}}$ that onsets at above 100 K. This result provides an example of the antiferromagnetic order in a pure $\ensuremath{\pi}$-electron system in $M$(${\mathrm{tmdt})}_{2}$, and it demonstrates that correlation among the $\ensuremath{\pi}$ electrons is so strong as to give the N\'eel temperature over 100 K. The small and inhomogeneous moments are understandable as the crucial disorder effect in correlated electrons situated near the Mott transition.

Quantitative Determination of Wax Contamination in Polystyrene HIPE Foam Using Solid-State NMR

Differences in molecular mobility between polystyrene foam and Brij-78 wax results in vast differences in the 1H nuclear magnetic resonance (NMR) linewidth. This allows for the convenient determination of wax content in the polystyrene foam components of inertial confinement fusion targets via solid-state NMR. Contamination levels as low as 0.1% are easily recognized and quantified, and the detection limit is calculated to be 0.02% even when only 32 transients are recorded.

Invited Review Article: Instrumentation for nuclear magnetic resonance in zero and ultralow magnetic field.

We review experimental techniques in our laboratory for nuclear magnetic resonance (NMR) in zero and ultralow magnetic field (below 0.1 μT) where detection is based on a low-cost, non-cryogenic, spin-exchange relaxation free 87Rb atomic magnetometer. The typical sensitivity is 20-30 fT/Hz1/2 for signal frequencies below 1 kHz and NMR linewidths range from Hz all the way down to tens of mHz. These features enable precision measurements of chemically informative nuclear spin-spin couplings as well as nuclear spin precession in ultralow magnetic fields.

Superresolution optical magnetic imaging and spectroscopy using individual electronic spins in diamond

Nitrogen vacancy (NV) color centers in diamond are a leading modality for both superresolution optical imaging and nanoscale magnetic field sensing. In this work, we address the key challenge of performing optical magnetic imaging and spectroscopy selectively on multiple NV centers that are located within a diffraction-limited field-of-view. We use spin-RESOLFT microscopy to enable precision nanoscale mapping of magnetic field patterns with resolution down to ~20 nm, while employing a low power optical depletion beam. Moreover, we use a shallow NV to demonstrate the detection of proton nuclear magnetic resonance (NMR) signals exterior to the diamond, with 50 nm lateral imaging resolution and without degrading the proton NMR linewidth.

Nonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectra.

According to the damped quantum rotation (DQR) theory, hindered rotation of methyl groups, evidenced in nuclear magnetic resonance (NMR) line shapes, is a nonclassical process. It comprises a number of quantum-rate processes measured by two different quantum-rate constants. The classical jump model employing only one rate constant is reproduced if these quantum constants happen to be equal. The values of their ratio, or the nonclassicallity coefficient, determined hitherto from NMR spectra of single crystals and solutions range from about 1.20 to 1.30 in the latter case to above 5.0 in the former, with the value of 1 corresponding to the jump model. Presently, first systematic investigations of the DQR effects in wide-line NMR spectra of a powder sample are reported. For 1,1,1-triphenylethane deuterated in the aromatic positions, the relevant line-shape effects were monitored in the range 99-121 K. The values of the nonclassicality coefficient dropping from 2.7 to 1.7 were evaluated in line shape fits to the experimental powder spectra from the range 99-108 K. At these temperatures, the fits with the conventional line-shape model are visibly inferior to the DQR fits. Using a theoretical model reported earlier, a semiquantitative interpretation of the DQR parameters evaluated from the spectra is given. It is shown that the DQR effects as such can be detected in wide-line NMR spectra of powdered samples, which are relatively facile to measure. However, a fully quantitative picture of these effects can only be obtained from the much more demanding experiments on single crystals.

Copper dynamics and structural-transformation in noble metal chalcogenides CuAgS probed by 63Cu NMR

Atomic-scale dynamics of a representative noble metal chalcogenide superionic conductor, stromeyerite (CuAgS), were examined by nuclear magnetic resonance (NMR) spectroscopy at various temperatures. Motional narrowing of 63Cu NMR line width was found in its cubic phase, demonstrating copper ions start diffusing via a hopping process. Moreover, the absence of 63Cu NMR signal in its orthorhombic or hexagonal phases was discussed, which could be well explained by copper ordering and reduced local symmetry at copper sites. The above NMR results are relevant for understanding its electron-crystal phonon-liquid behaviors and transient structure-transformation, which are associated with extremely low thermal conductivities and abnormal change of thermal power during superionic phase transition in this material.

Charge Variations in Cuprate Superconductors from Nuclear Magnetic Resonance

Charge inhomogeneities in the cuprates were reported early on and have been in the focus of much research recently. Nuclear magnetic resonance (NMR) is very sensitive to local charge symmetry through the electric quadrupole interaction that must detect any static charge density variation. Recent experiments in high magnetic fields that seem to induce charge density waves in some systems have rekindled the interest in static inhomogeneities. It has long been known that excessive NMR linewidths can be observed in all cuprates, but with the exception of a few materials. However, the relation of the quadrupolar linewidths with respect to variations of the charge density in the cuprates is not understood. Here, we investigate YBa2Cu3O7 and we find even in a moderate magnetic field that below about 200 K, i.e., well above T c, a temperature dependent NMR linewidth appears that must be related to incipient static charge density variations. We argue that this establishes field induced charge density variation as a more general phenomenon in the cuprates. In view of the very recent understanding of the relation between the hole distribution in the CuO2 plane and T c, it is argued that charge density variations are ubiquitous, but appear not related to the maximum T c.

Competing effects of Mn and Y doping on the low-energy excitations and phase diagram ofLa1−yYyFe1−xMnxAsO0.89F0.11iron-based superconductors

Muon Spin Rotation ($\mu$SR) and $^{19}$F Nuclear Magnetic Resonance (NMR) measurements were performed to investigate the effect of Mn for Fe substitutions in La$_{1-y}$Y$_{y}$Fe$_{1-x}$Mn$_x$AsO$_{0.89}$F$_{0.11}$ superconductors. While for $y = 0$ a very low critical concentration of Mn ($x = 0.2$%) is needed to quench superconductivity, as $y$ increases the negative chemical pressure introduced by Y for La substitution stabilizes superconductivity and for $y= 20$% it is suppressed at Mn contents an order of magnitude larger. A magnetic phase arises once superconductivity is suppressed both for $y$=0 and for $y= 20$%. Low-energy spin fluctuations give rise to a peak in $^{19}$F NMR $1/T_1$ with an onset well above the superconducting transition temperature and whose magnitude increases with $x$. Also the static magnetic correlations probed by $^{19}$F NMR linewidth measurements show a marked increase with Mn content. The disruption of superconductivity and the onset of the magnetic ground-state are discussed in the light of the proximity of LaFeAsO$_{0.89}$F$_{0.11}$ to a quantum critical point.

2H nuclear magnetic resonance study of deuterated water dynamics in perfluorosulfonic acid ionomer Nafion

We have employed deuteron nuclear magnetic resonance (NMR) spectroscopy in order to study the dynamics of the deuterated water (D2O) molecules introduced into a perfluorosulfonic acid ionomer Nafion (NR-211) film. According to the 2H NMR spectral analysis, the deuterated water molecules at low temperatures occupied either relatively rigid or mobile sites up to the temperature TM=240K where all the deuterated water molecules became mobile. The temperature-dependent NMR linewidths sensitively reflected the motional narrowing of the rigid and mobile sites, and the NMR chemical shift reflected significant changes in the hydrogen bonds of the deuterated water. While a slow- to fast-limit motional transition was manifested at TM in the laboratory-frame NMR spin–lattice relaxation, the rotating-frame spin–lattice relaxation indicated no bulk liquid water state down to 200K.

11B pulsed nuclear magnetic resonance study of DyNi2B2C single crystals

DyNi2B2C is the only compound in the RNi2B2C (R = rare-earth element) series where superconductivity at Tc ∼6.2 K coexists with the antiferromagnetic ordering below the Nèel temperature TN ∼10.3 K. This system is of great interest because superconductivity rarely coexists with magnetic ordering. 11B pulsed nuclear magnetic resonance (NMR) measurements were performed at 8.0056 T to investigate the local electronic structures and 4f spin dynamics of DyNi2B2C powders and single crystals. The spectrum for the single crystal showed three narrow resonance peaks at 295 K due to the nuclear Zeeman splitting of a nuclear spin I = 3/2 with quadrupolar perturbation. The 11B NMR Knight shift of the single crystal was very large and highly anisotropic at K = −0.60% and +0.27% for the fields parallel and perpendicular, respectively, to the c-axis at 295 K. Considering the anisotropy of the Knight shift, we were able to simulate the 11B NMR power pattern that agreed well with the measured spectrum. The linewidth for DyNi2B2C was also large and anisotropic, and the linewidth value increased rapidly at low temperatures. The 11B NMR shift and linewidth were found to be proportional to the magnetic susceptibility, indicating that the hyperfine field at the B site originates from the 4f spins of Dy. Above TN, the values for 1/T1 (the spin-lattice relaxation rate) and 1/T2 (the spin-spin relaxation rate) were very large, showing slight increases at low temperatures. Below TN, the values of 1/T1 and 1/T2 were suppressed significantly because of the slowing of the 4f spin fluctuation. This confirmed the huge change in Dy 4f spin dynamics across the antiferromagnetic transition.

Major Variations in HIV-1 Capsid Assembly Morphologies Involve Minor Variations in Molecular Structures of Structurally Ordered Protein Segments

We present the results of solid state nuclear magnetic resonance (NMR) experiments on HIV-1 capsid protein (CA) assemblies with three different morphologies, namely wild-type CA (WT-CA) tubes with 35-60 nm diameters, planar sheets formed by the Arg(18)-Leu mutant (R18L-CA), and R18L-CA spheres with 20-100 nm diameters. The experiments are intended to elucidate molecular structural variations that underlie these variations in CA assembly morphology. We find that multidimensional solid state NMR spectra of (15)N,(13)C-labeled CA assemblies are remarkably similar for the three morphologies, with only small differences in (15)N and (13)C chemical shifts, no significant differences in NMR line widths, and few differences in the number of detectable NMR cross-peaks. Thus, the pronounced differences in morphology do not involve major differences in the conformations and identities of structurally ordered protein segments. Instead, morphological variations are attributable to variations in conformational distributions within disordered segments, which do not contribute to the solid state NMR spectra. Variations in solid state NMR signals from certain amino acid side chains are also observed, suggesting differences in the intermolecular dimerization interface between curved and planar CA lattices, as well as possible differences in intramolecular helix-helix packing.

Low temperature magnetic properties and spin dynamics in single crystals of Cr8Zn antiferromagnetic molecular rings.

A detailed experimental investigation of the effects giving rise to the magnetic energy level structure in the vicinity of the level crossing (LC) at low temperature is reported for the open antiferromagnetic molecular ring Cr8Zn. The study is conducted by means of thermodynamic techniques (torque magnetometry, magnetization and specific heat measurements) and microscopic techniques (nuclear magnetic resonance line width, nuclear spin lattice, and spin-spin relaxation measurements). The experimental results are shown to be in excellent agreement with theoretical calculations based on a minimal spin model Hamiltonian, which includes a Dzyaloshinskii-Moriya interaction. The first ground state level crossing at μ0Hc1 = 2.15 T is found to be an almost true LC while the second LC at μ0Hc2 = 6.95 T has an anti-crossing gap of Δ12 = 0.19 K. In addition, both NMR and specific heat measurements show the presence of a level anti-crossing between excited states at μ0H = 4.5 T as predicted by the theory. In all cases, the fit of the experimental data is improved by introducing a distribution of the isotropic exchange couplings (J), i.e., using a J strain model. The peaks at the first and second LCs in the nuclear spin-lattice relaxation rate are dominated by inelastic scattering and a value of Γ ∼ 10(10) rad/s is inferred for the life time broadening of the excited state of the open ring, due to spin phonon interaction. A loss of NMR signal (wipe-out effect) is observed for the first time at LC and is explained by the enhancement of the spin-spin relaxation rate due to the inelastic scattering.