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The anisotropic susceptibility of YBa 2 Cu 3 O x (6.46⪕ x ⪕6.98) has been measured as a function of oxygen composition. Samples were prepared by a high temperature zirconium-getter annealing technique followed by magnetic orientation in epoxy. The normal state magnetic susceptibility was found to be weakly dependent on temperature. The room temperature values of the susceptibility decrease linearly as the oxygen composition decreases, whereas the difference in susceptibilities for magnetic fields parallel and perpendicular to the c -axis is nearly constant. This suggests that in this range of oxygen composition the susceptibility anisotropy comes mostly from the anisotropic part of the Van Vleck susceptibility and the spin susceptibility remains nearly isotropic. Neutron diffraction results show a significant oxygen occupancy at the O(5) site. Nuclear quadrupolar and magnetic resonance spectra of the plane copper indicate a marked degree of electronic disorder, confirming that there are microscopic structural effects from the high temperature zirconium-getter annealing procedure.

The synthesis of layered cuprates with nonmagnetic and fixed oxidation state cations separating CuO planes has, until now, led to nonsuperconducting materials. Recently we were able to introduce superconductivity in YSrCuGaO system by appropriate doping and annealing.

The 63 Cu NMR spin-lattice relaxation rate of YBa 2 Cu 3 O 6.98 (T C =93.3K) at the plane site shows classic Korringa temperature dependence in the normal state with T 1 T=230±20 Kms. This resuit is consistent with Fermi quasi-particle character of the low lying electronic excitations near the Fermi energy. Precursory behavior is observed just above T c in the relaxation data. This may be consistent with order parameter fluctuations.

Trigonal ordering is evident from electron microscopy of quenched powders of composition YBa 2 Cu 3 O 6.5 . The powders are a mixture of phases, some of which are based upon two trigonal phases with a = 0.54 and c = 0.66 nm. In the first the yttrium and barium atoms order on the (111) planes of the parent perovskite structure rather than the (001) while in the second stacking sequence the yttrium layer of this structure is interchanged with one of the copper layers.