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In previous 29Si NMR basal-plane field rotation measurements, a modest breaking of the fourfold symmetry was suggested in the hidden-order state of URu2Si2. Here, the angular dependence of the 29Si NMR linewidth is analyzed in detail, indicating the occurrence of a distribution of twofold local fields at the Si sites even in a high-quality single crystal. The relation between sample quality and the occurrence of effects having twofold symmetry is discussed. [ABSTRACT FROM AUTHOR]

Recently there is renewed interest in quantum critical phase transitions (QCPT) at T = 0 K in metallic strongly correlated electron systems. From early experimental results, the QCPT in the Kondo-lattice compound YbRh2Si2 is not a case of the ordinary spin density wave (SDW) instability observed in Ce-based Kondo lattices, but a candidate for a novel locally critical case. Here, we observe that coexisting, static Fermi liquid (FL) and non-Fermi liquid (NFL) states are a key feature of the QCPT in YbRh2Si2. By means of nuclear magnetic resonance (NMR) spin-lattice relaxation time (T1) measurements on a single-crystalline sample, we find that the FL and NFL states are invariant, whereas their ratio in a crossover is field dependent near the QCPT. Such a pair of states has remained hidden in Ce compounds, owing presumably to the short lifetimes of the two states. We derive a scaling law for the occupation ratio of the two states, which could be widely applicable to Kondo-lattice systems. [ABSTRACT FROM AUTHOR]

Very high field 29Si-NMR measurements using a fully 29Si-enriched URu2Si2 single crystal were carried out in order to microscopically investigate the "hidden order" (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the 29Si shift, 29Kc. Moreover, a strong enhancement of 29Kc develops near a critical field Hc≃35.6 T, and the 29Si-NMR signal disappears suddenly at Hc, indicating the total suppression of the HO state. Nevertheless, a weak and shifted 29Si-NMR signal reappears for fields higher than Hc at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) studies using 11B and 69,71Ga have been performed on the tetragonal Ce-based ferromagnet CeRu2Ga2B. The Knight shifts for the nuclei show an Ising-type anisotropy along the c axis, similar to results from the static susceptibility. From the Knight shift measurements, the hyperfine coupling constants have been determined. The anisotropy of the spin-lattice relaxation rates l/T1, indicates that the anisotropy of spin fluctuations are also Ising-like along the c axis. The localized character of the 4ƒ electrons in this system is discussed. [ABSTRACT FROM AUTHOR]

Zero-field 115In-nuclear magnetic resonance (NMR) has been used to study single crystals of CePt2In7, a heavy-fermion antiferromagnet with a Néel temperature (TN) of 5.2 K at ambient pressure. Narrow linewidths of 115In-nuclear quadrupolar resonance spectra are observed from each of three crystallographically inequivalent In(1), In(2), and In(3) sites. The NMR spectra under zero field near the 3?Q line of the orthorhombic In(3) sites are tracked by temperatures down to 1.6 K and by hydrostatic pressures up to 2.4 GPa. These data reveal the coexistence of commensurate and incommensurate antiferromagneic orders at ambient pressure and that the commensurate ordering is stabilized by increasing pressures where bulk superconductivity emerges. [ABSTRACT FROM AUTHOR]

Abstract: We have performed 17O NMR spin–lattice relaxation measurements with conventional NMR techniques on 17O in . The results have been found to exhibit a field-dependent cross-relaxation effect from 237Np in addition to the field-independent exchange-fluctuation background rate which dominates at high fields. Analysis of the cross-relaxation process reveals a temperature-independent relaxation rate as well as a greatly enhanced unlike spin–spin coupling between the 237Np spins and their 17O nearest neighbors. We discuss the possibility of observing the cross-relaxation effects in other actinide dioxides. [Copyright &y& Elsevier]

Abstract: NMR measurements have been performed on a series of the actinide dioxides, UO2, NpO2 and PuO2. Although the NMR spectra in these materials are similar at higher temperatures, the low-temperature spectra present are significantly different. In UO2 we have observed a wide spectrum, forming a rectangular shape below  K. In NpO2, on the other hand, the spectra broaden rather gradually and exhibit a two-peak structure below  K. In PuO2, neither spectrum broadening nor splitting has been observed. We show that these NMR spectra clearly indicate the different nature of the low-temperature magnetic ground states in these actinide compounds. [Copyright &y& Elsevier]

Abstract: We report NMR measurements in a single crystal of . We have observed oscillatory spin–echo decay for certain O sites below . These spin–echo oscillations are well understood in terms of an axially symmetric electric field gradient created by a longitudinal triple-q antiferro-quadrupolar ordering. In the present work, we show that direct observation of the quadrupolar order parameters is possible by means of NMR. [Copyright &y& Elsevier]

Abstract: In order to elucidate the nature of the exotic ordered phase of NpO below , we have initiated the first O-NMR measurements. From the temperature dependence of the O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below . This finding verifies the lowering of symmetry in the ordered state of NpO. [Copyright &y& Elsevier]

Abstract: We have initiated the first O-NMR measurements in the ordered state of NpO. From the O-NMR spectrum, we have confirmed the occurrence of two inequivalent oxygen sites below . It has also been shown that the O-NMR spectrum in the ordered state can be understood by considering an unconventional hyperfine interaction between the O nuclear spins and field-induced antiferromagnetic moments arising from the longitudinal triple- antiferro-quadrupolar order. These NMR results give strong evidence for the occurrence of the longitudinal triple- multipole structure in NpO. [Copyright &y& Elsevier]

We report a coexistence of superconductivity and antiferromagnetism in HgBa2Ca4Cu5Oy with Tc=108 K trough Cu-NMR measurements. This compound is composed of two kinds of CuO2 planes in a unit cell, three inner planes (IP) and two outer planes (OP). The OP is optimally-doped, undergoing a superconducting transition at Tc=108 K, whereas the IP is strongly underdoped, doing an antiferromagnetic transition below TN∼60 K. [Copyright &y& Elsevier]

The antiferromagnet URhIn5 with the Néel temperature TN = 98 K has been investigated by nuclear magnetic/quadrupole resonance (NMRJNQR). 115In-NQR spectra in the paramagnetic state give the respective electrical field gradient parameters for the locally tetragonal and orthorhombic In(1) and In(2) sites. In the antiferromagnetic state at 4.5 K, 115In-NMR spectra in the zero external field mdicate a commensurate antiferromagnetic structure. The internal field at In(1) sites is found to be zero and that at In(2) sites is 21.1 kOe at 4.5 K. The temperature (T) dependence of the nuclear relaxation rates 1/ T1 in the paramagnetic state shows a distinct site dependence: Korringa-type constant (T1 T)-1 behavior below ∼150 K for In(1) sites and a divergent behavior of 1/ T1 toward TN for In(2). The plausible antiferromagnetic structure is discussed based on these observations. [ABSTRACT FROM AUTHOR]

Abstract: We present 27Al NMR studies for a single crystal of the Np-based superconductor NpPd5Al2 . We have observed a five-line 27Al NMR spectrum with a center line and four satellite lines separated by first-order nuclear quadrupole splittings. The Knight shift clearly drops below . The temperature dependence of the 27Al nuclear spin-lattice relaxation rate shows no coherence peak below , indicating that NpPd5Al2 is an unconventional superconductor with an anisotropic gap. The analysis of the present NMR data provides evidence for strong-coupling d-wave superconductivity in NpPd5Al2. [Copyright &y& Elsevier]

Abstract: Nuclear quadupole resonance (NQR) measurements have been performed on the Pu-based superconductor with a transition temperature of . NQR lines ascribed to , , and have been found in zero field. Spin–lattice relaxation rate () data for these lines have been measured in the superconducting state. The temperature variation of can be interpreted in terms of a line-nodal superconducting gap. Data for both the and NQR lines show a constant- behavior between and , which suggests that a coherent Fermi-liquid state sets in below . The modified Korringa relation using and Knight shift data in an applied field indicates that the normal state of can be regarded as an antiferromagnetically correlated metal. [Copyright &y& Elsevier]

Abstract: We report NMR measurements in isostructural compounds (: 115 type) (An: U, Np and Pu, T: Fe, Co and Pt) with different ground states (paramagnet, antiferromagnet and superconductor) using single crystal samples. The electrical field gradient at the Ga and Co sites are similar in all compounds, indicating that the charge distribution around these sites is determined mainly by intra-atomic orbitals. In contrast, the hyperfine coupling constants at the Ga and Co sites depend on the compounds considerably. Since the hyperfine coupling at the ligand sites is a transferred hyperfine coupling due to hybridization between 5f and ligand orbitals, it is natural that the hyperfine coupling constant depends on the 5f electronic states. Spin–lattice relaxation rates in the paramagnetic state show more drastic differences between the compounds. In the antiferromagnets , and , shows a Curie–Weiss behavior at high temperatures, indicating a strong localized character. By contrast, in the paramagnet is small and almost independent of T, indicating an ordinary metallic state with weak exchange enhancement. Finally, in the superconductor the magnitude of lies between those of the antiferromagnets and the paramagnet. [Copyright &y& Elsevier]

In order to identify the spin contribution to superconducting pairing compatible with the so-called "hidden order", 29Si nuclear magnetic resonance measurements have been performed using a high-quality single crystal of URu2Si2. A clear reduction of the 29Si Knight shift in the superconducting state has been observed under a magnetic field applied along the crystalline c axis, corresponding to the magnetic easy axis. These results provide direct evidence for the formation of spin-singlet Cooper pairs. Consequently, results indicating a very tiny change of the in-plane Knight shift reported previously demonstrate extreme uniaxial anisotropy for the spin susceptibility in the hidden order state. [ABSTRACT FROM AUTHOR]

Abstract: We report 11B NMR results on , which is an enhanced Pauli paramagnet with electronic specific heat coefficient . The Knight shift and nuclear spin-lattice relaxation measurement revealed two distinct temperature (T) regimes, in which the magnetic state dynamics are different one another. From the standpoint of general susceptibility , we suggest that ferromagnetic (FM) correlations is dominant in high T-region, on the other hand, antiferromagnetic (AFM) correlations emerge below . Since does not show the tendency to disappear its magnitude at , FM correlations still survive with AFM correlations even in the low-T state. [Copyright &y& Elsevier]