Morphology and physical properties of mono(YBa2Cu3O7) and multilayered (YBa2Cu3O7/SmBa2Cu3O7/ YBa2Cu3O7) superconducting thin films with thickness ranging from 90 nm to 28 nm have been investigated. For both types of samples, the superconducting properties degraded with reduction of film thickness. Structural and electromagnetic properties were visualized through scanning electron microscopy an...

Well-defined zigzag-shaped ramp-type Josephson junctions between YBa2Cu3O7 and Nb have been studied. The magnetic field dependencies of the critical currents provide evidence for d-wave--induced alternations in the direction of the Josephson current between neighboring sides of the zigzag structure. The arrays present controllable model systems to study the influences of pi facets in high-angle...

We report on an ab anisotropy of Jc parallel b/Jc parallel a approximately/= 1.8 IcRn parallelb/IcRn parallel a approximately/= 1.2 and in ramp-edge junctions between untwinned YBa2Cu3O7 and s-wave Nb. For these junctions, the angle theta with the YBa2Cu3O7 crystal b axis is varied as a single parameter. The RnA(theta) dependence presents twofold symmetry. The minima in IcRn at theta approximat...

We show magnetoresistance in excess of 1000% in trilayers containing highly spin-polarized La0.7Ca0.3MnO3 and high-Tc superconducting YBa2Cu3O7. This large magnetoresistance is reminiscent of the giant magnetoresistance (GMR) in metallic superlattices but with much larger values, and originates at spin imbalance due to the injection of spin-polarized carriers. Furthermore, in contrast to ordina...

Charge neutrality and stoichiometry impose severe restrictions on the mechanisms of epitaxial growth of complex oxides. The fundamental question arises of what is the minimum growth unit when sample thickness is reduced beyond the size of the unit cell. We have investigated the growth mechanism of YBa2Cu3O7 cuprate superconductor, using a consistent approach based on the growth of noninteger nu...

The microwave surface impedance = + 0 of MgB2 thin films was measured via advanced dielectric resonator (DR) techniques. First, the temperature dependence of the penetration depth measured with a sapphire puck at 17.9 GHz can be well fitted from 5 K close to by the standard BCS integral expression assuming the reduced energy gap (0) to be as low as 1.0–1.1 assuming (0) = 100–110 nm. These resul...

The magnetic susceptibility of underdoped yttrium and lanthanum cuprates is interpreted based on the self-consistent solution of the t-J model of a Cu-O plane. The calculations reproduce correctly the frequency dependencies of the susceptibility in YBa2Cu3O7−y and La2−xSrxCuO4 attributing their dissimilarity to the difference in the damping of spin excitations. In YBa2Cu3O7−y these excitations ...

Submitted for the MAR08 Meeting of The American Physical Society Electrical Transport Properties of Nanostructured YBa2Cu3O7−δ Rings and Wires1 P. MORALES, J.Y.T. WEI, Dept. of Physics, University of Toronto, P.C. KUO, J. SHIUE, M.K. WU, Institute of Physics, Academia Sinica Taiwan — The resistance and current-voltage characteristics of nanostructured high-Tc superconducting YBa2Cu3O7−δ rings a...