We report measurements of the thermoelectric power S and resistivity ρ{variant} of high-Tc superconductors RBa2Cu3Ox. For R=Y or a rare earth and x{reversed tilde equals}7, S is positive and nearly temperature independent but its magnetude can vary depending on R. We have systematically varied the oxygen stoichiometry (6

Electrical resistivity, thermoelectric power, magnetic susceptibility and neutron scattering experiments on YBa2-yLayCu3Ox, with y = 1, show that this compound is neither superconductive nor magnetically ordered but are consistent with it being an electronically localized system. © 1988.

We track the systematic variation in magnetic susceptibility (χ), thermal conductivity (κ), anisotropic resistivity (ρ{variant}), and thermoelectric power (S) of crystalline La2CuO4+δ as a function of light hole doping. The level of hole doping (δ) was carefully varied by anneals under controlled oxygen-partial-pressure performed in such a way that the antiferromagnetic ordering temperature TN ranged from 250 to 310 K. χ data indicate that increased oxygen hole doping acts to reduce TN below the δ = 0 value of 320 K. Anomalies are present in κ at Tn that result from Cu spin fluctuations about the magnetically ordered ground state. Anomalies are also present in ρ{variant} and S that occur at TN for air-annealed samples wherein TN = 250 K; when more lightly hole-doped so that TN >250 K, the anomalies in ρ{variant} and S do not occur at TN, but instead occur at T<250 K. In analogy with heavily oxygen-loaded La2CuO4+δ, these transport anomalies may result from phase separation involving the diffusion of non-stoichiometric, excess oxygen. © 1991.

We have measured the electrical resistivity, thermoelectric power, magnetic susceptibility, Hall coefficient and upper critical field near Tc in EuBa2Cu3Ox, where 6.09

We have studied the x-ray-absorption near-edge spectra of EuBa2(Cu1-yZny)3O7 as a function of Zn and O content. There is clear evidence for the development of Cu1+ ions as the O content is reduced to levels sufficient to suppress superconductivity. However, there is no effect on the electronic state of the Cu ion as the Zn content is increased and superconductivity vanishes. We tentatively conclude that the suppression of superconductivity is in both cases due to the preferred occupancy of certain planes by nonmagnetic (filled d subshell) atoms, as proposed in YBa2Cu3O6 on the basis of neutron scattering. © 1988 The American Physical Society.

We have measured resistivity ρ components both parallel and perpendicular to the Cu-O planes in single-crystalline La2CuO4. Substantial anisotropy, reaching values as large as 103, is observed in the resistivity. The temperature dependence of ρ, together with Hall effect and thermoelectric power measurements, suggests hopping conduction between localized states at low temperatures, with diffusive transport at higher temperatures. These results are in contradistinction to previous reports. © 1988 The American Physical Society.

We report electrical resistance and magnetoresistance measurements on EuBa2(Cu1-yZny)3Ox under pressures to 17 kbar. With Zn substitution, Tc is depressed rapidly (∼19 K/ at.% Zn) and there are qualitative changes in the temperature and field response of the resistance. Pressure drives the Zn-substituted samples toward undoped EuBa2Cu3Ox behavior. Analysis of the temperature dependent resistance for y=0.05 and P=0, together with Hall effect and thermopower data, suggests that the suppression of superconductivity may arise from weak three-dimensional localization promoted by Coulomb interactions. © 1987.

Resistivity, thermoelectric power, Hall effect, and magnetic susceptibility measurements are reported in the normal state of the high-Tc compounds YBa2Cu3O7-y and GdBa2Cu3O7-y. The results are different from those expected for an uncorrelated metallic band. We suggest that Coulomb interactions are important and that the interaction energy is comparable to or larger than the uncorrelated bandwidth, leading to moderately heavy-fermion-like behavior in the normal state. The Sommerfeld coefficient calculated from the susceptibility indicates that the electron-phonon coupling constant at Tc is not unusually large. © 1987 The American Physical Society.