We report NMR measurements of the nuclear relaxation rate at all copper and oxygen sites in magnetically aligned powder samples of YBa2Cu3O7. There is no peak in the oxygen relaxation rate below Tc at any oxygen site supporting the possibility that d-wave pairs are formed in the superconducting state. Comparison of the oxygen and copper rates in the planes reveals a characteristic temperature greater than Tc. © 1989.

We report NMR measurements of the nuclear relaxation rate at all copper and oxygen sites in magnetically aligned powder samples of YBa2Cu3O7. Comparison of the oxygen and copper relaxation reveals a characteristic temperature greater than Tc. The copper relaxation rate is enhanced by antiferromagnetic copper spin fluctuations which are undiminished in the superconducting state. The absence of a coherence peak indicates that the superconductive pairing is not of the conventional BCS type. © 1989 The American Physical Society.

We have measured the copper nuclear relaxation rate in GdBa2Cu3O7 in zero applied field using nuclear quadrupole resonance. Fluctuations in the 4f moment associated with the gadolinium contribute strongly to the copper relaxation rate, and this contribution will depend strongly on the copper-gadolinium separation. This separation differs considerably for the two copper sites. Comparison of the relaxation rates shows that the copper signal at the higher frequency (32 MHz) originates from the Cu(2) site, which is located closer to the gadolinium than is the Cu(1) site. © 1988 The American Physical Society.

The Cu63 Knight shift in YBa2Cu3O7 has been measured at both Cu(1) (chain) and Cu(2) (plane) sites, using a uniaxially aligned powder. The isotropic part of the spin Knight shift (Ks) was found to be positive for both sites, suggesting large transferred hyperfine fields from oxygen p states. The Knight shifts at both sites show significant change below Tc, indicating important roles of both the planes and chains in the superconductivity. Despite the uncertainty in the diamagnetic screening, the axial part of Ks at Cu(2) sites is found to show linear-T behavior at low temperatures. © 1989 The American Physical Society.

O17 nuclear-magnetic-resonance spectra are obtained, using uniaxially aligned powder of YBa2Cu3O7, and resonance lines from the four inequivalent oxygen sites are clearly distinguished. Principal components of the electric field gradient (EFG) and the shift tensors are obtained in the normal state. Assigning the direction of the largest EFG components of Cu-O bond axes, the anisotropy of the shift suggests that the spin density at the plane O(2,3) and the bridging O(4) sites resides on the p orbitals. The domonant contribution to the spin susceptibility comes from Cu d states. © 1989 The American Physical Society.

139La nuclear quadrupole resonance measurements in lightly doped La2Cu1-xLixO4 have been performed to reveal the dependence of the magnetic properties of the antiferromagnetic CuO2 planes on the character of the doped holes and their interactions with the dopant. A detailed study shows that the magnetic properties are remarkably insensitive to the character of the dopant impurity. This indicates that the added holes form previously unrecognized collective structures. © 1998 The American Physical Society.

The microscopic magnetic properties of the CuO2 planes in YBa2Cu3O6.63 (Tc=62 K) have been investigated in Cu and O NMR experiments. Unlike the fully oxygenated Y-Ba-Cu-O7 (Tc 90 K), the various components of the Cu and O Knight-shift tensors show strong but identical temperature dependences in the normal state. This supports the picture that there is only one spin component in the CuO2 planes. The spin susceptibility deduced from Knight-shift results shows significant reduction with decreasing temperature in the normal state. The temperature dependences of the nuclear-spin-relaxation rates (1/T1) are very different for the Cu and the O sites. 1/(T1T) at the O sites is nearly proportional to the spin susceptibility. 1/(T1T) at the Cu sites shows a broad peak around 150 K. We discuss these relaxation behaviors based on a model of the dynamical spin susceptibility proposed by Millis, Monien, and Pines. © 1991 The American Physical Society.

We present our 17O NMR experimental results in a magnetically aligned powder sample of YBa2Cu3O7-δ (Tc = 93 K). The sign of the anisotropic Knight shift shows that the spin density resides mainly on the pσ orbitals at the planar O(2,3) and bridging O(4) sites. About 30 % of the total spin susceptibility is attributed to the oxygen 2pσ states. The Knight shift at the O(2,3) sites decrease more rapidly than that at the chain O(1) sites, indicating a larger gap in the planes. The nuclear relaxation rate at the O(2,3) sites shows linear-T (Korriga) behavior above Tc, in contrast to the much weaker temperature dependence at the planar Cu(2) sites. However, these two rates show identical temperature dependence below about 110 K, indicating that an important change in the spin dynamics takes place above Tc. © 1989.

We report 115In nuclear quadrupolar resonance measurements of the heavy fermion compound CeRhIn5 in the paramagnetic and antiferromagnetic states. The magnetic order is consistent with a model of helical modulation of the Ce moments that is incommensurate with the lattice, and the magnetic dynamics indicate possible two-dimensional behavior.