The microscopic magnetic properties of the Cu02 planes in YBa2Cu306 63 (T, =62 K) have been investigated in Cu and 0 NMR experiments. Unlike the fully oxygenated Y-Ba-Cu-07 (T, =90 K), the various components of the Cu and 0 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 Cu02 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/T& ) are very different for the Cu and the 0 sites. 1/( T& T) at the O sites is nearly proportional to the spin susceptibility. 1/(T& T) 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.

Puzzling aspects of high-transition-temperature (high-Tc) superconductors include the prevalence of magnetism in the normal state and the persistence of superconductivity in high magnetic fields. Superconductivity and magnetism generally are thought to be incompatible, based on what is known about conventional superconductors. Recent results, however, indicate that antiferromagnetism can appear in the superconducting state of a high-Tc superconductor in the presence of an applied magnetic field. Magnetic fields penetrate a superconductor in the form of quantized flux lines, each of which represents a vortex of supercurrents. Superconductivity is suppressed in the core of the vortex and it has been suggested that antiferromagnetism might develop there. Here we report the results of a high-field nuclear-magnetic-resonance (NMR) imaging experiment in which we spatially resolve the electronic structure of near-optimally doped YBa2Cu3O7-delta inside and outside vortex cores. Outside the cores, we find strong antiferromagnetic fluctuations, whereas inside we detect electronic states that are rather different from those found in conventional superconductors.

We present a manometer designed to measure pressures of 1–20 kbar in temperatures between 4–300 K in cylinder-piston type chambers, with an accuracy of ∼100 bar. The manometer is based on pressure-dependent zero-field 63Cu nuclear quadrupole resonance frequency corresponding to ‖±3/2〉↔‖±1/2〉 transition in Cu2O. The nuclear quadrupole resonance frequency νQ varies linearly with pressure and its temperature dependence is adequately explained by a model of lattice vibrational modes in O—Cu—O bonds. This manometer is particularly convenient for zero or high-field magnetic resonance experiments.

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