Interlayer coupling effect in high-Tc superconductors probed by YBa2Cu3O7-x/PrBa2Cu3O7-x superlattices

Effect of interface-induced exchange fields on cuprate-manganite spin switches

We examine the anomalous inverse spin switch behavior in La0.7Ca0.3MnO3(LCMO)/YBa2Cu3O7-δ (YBCO)/LCMO trilayers by combined transport studies and polarized neutron reflectometry. Measuring magnetization profiles and magnetoresistance in an in-plane rotating magnetic field, we prove that, contrary to many accepted theoretical scenarios, the relative orientation between the two LCMO's magnetizations is not sufficient to determine the magnetoresistance. Rather the field dependence of magnetoresistance is explained by the interplay between the applied magnetic field and the (exponential tail of the) induced exchange field in YBCO, the latter originating from the electronic reconstruction at the LCMO/YBCO interfaces.

Pulsed Laser Deposition of High Tc Superconducting thin Films: Present and Future

Pulsed laser deposition (PLD) has been widely used for deposition of high Tc superconducting thin films, and is recognized as one of the best physical vapor techniques for the preparation of these films. The most important advantage of this technique is stoichiometric deposition; films can be made with the same composition as the target. Utilizing PLD, not only thin films but also multilayers and superlattices of high Tc superconductors have been fabricated. In this paper, the performance of the technique will be reviewed, and speculations regarding the future would be made.

Evidence of Two-Dimensional Superconductivity in the Single Crystalline Nanohybrid of Organic-Bismuth Cuprate

A coordination compound of HgI(2)(pyridine)(2) can be successfully intercalated into a single crystalline Bi(2)Sr(2)CaCu(2)O(y) high-T(c) superconductor through an interlayer complexation reaction between pyridine molecules and bismuth cuprate pre-intercalated with mercuric iodide. X-ray diffraction and X-ray absorption spectroscopic results clearly demonstrate that the single crystalline nature of the pristine bismuth cuprate remains unchanged even after the intercalation of organic complex as well as those of iodine and mercuric iodide. According to the angle-dependent dc magnetization measurements, the intercalation of bulky organic molecules completely blocks superconductive currents along the c-axis, whereas a superconducting transition along the in-plane direction still occurs in the organic intercalate. In the case of the iodine or mercuric iodide intercalates with smaller lattice expansions, an out-of-plane diamagnetic transition is not wholly quenched but significantly depressed by the intercalation, confirming the reduction of interlayer interaction. The present finding can provide straightforward evidence of the two-dimensionality of high temperature superconductivity in the present cuprate-based nanohybrid material.

A Novel Hybrid of Bi-Based High-Tc Superconductor and Molecular Complex

Molecular complex HgI2Py2 (Py=pyridine) was intercalated into the Bi-based high-Tc cuprate by intercalative complexation. The intercalation method adopted in this work is based on the new concept, where a neutral ligating agent is diffused into the preintercalated HgI2 layer leading to a charge transfer-type complex formation between the Bi2O2 double layers of Bi2Sr2CaCu2Oy.

Very large purely intralayer critical current density in ultrathin cuprate artificial structures

Ultrathin artificial high temperature superconducting structures, consisting of (Ba(0.9)Nd0.1)CuO2+x and CaCuO2 layers, were grown by pulsed laser deposition. Intralayer superconductivity at 60 K was obtained for a structure consisting of a single (CaCuO2) block sandwiched between two (Ba(0.9)Nd0.1)CuO2+x charge reservoir blocks. The purely intralayer critical current density was measured at 4.2 K and resulted to be larger than 10(8) A/cm(2). These findings clearly show that interaction between nearest neighbor (CaCuO2) layers is not essential for high T(c) superconductivity and strongly supports the physical model based on the idea that intralayer interaction alone is responsible for high temperature superconductivity.

SCIENCE AND TECHNOLOGY OF HIGH-TEMPERATURE SUPERCONDUCTING FILMS

▪ Abstract  The field of high-temperature superconducting thin films is reviewed, focusing on the synthesis and properties of materials that are most promising for device applications. Current materials issues that are important for emerging device applications of oxide superconducting films are discussed, with emphasis on the growth, characterization, and use of epitaxial films. The status of specific superconducting device technologies is briefly reviewed.

High-Tc superconductors in the two-dimensional limit:

The free modulation of interlayer distance in a layered high-transition temperature (high-Tc) superconductor is of crucial importance not only for the study of the superconducting mechanism but also for the practical application of high-Tc superconducting materials. Two-dimensional (2D) superconductors were achieved by intercalating a long-chain organic compound into bismuth-based high-Tc cuprates. Although the intercalation of the organic chain increased the interlayer distance remarkably, to tens of angstroms, the superconducting transition temperature of the intercalate was nearly the same as that of the pristine material, suggesting the 2D nature of the high-Tc superconductivity.

Synthesis of Novel Thin-Film Materials by Pulsed Laser Deposition

Pulsed laser deposition (PLD) is a conceptually and experimentally simple yet highly versatile tool for thin-film and multilayer research. Its advantages for the film growth of oxides and other chemically complex materials include stoichiometric transfer, growth from an energetic beam, reactive deposition, and inherent simplicity for the growth of multilayered structures. With the use of PLD, artificially layered materials and metastable phases have been created and their properties varied by control of the layer thicknesses. In situ monitoring techniques have provided information about the role of energetic species in the formation of ultrahard phases and in the doping of semiconductors. Cluster-assembled nanocrystalline and composite films offer opportunities to control and produce new combinations of properties with PLD.

Superconductivity in SrCuO 2 -BaCuO 2 Superlattices: Formation of Artificially Layered Superconducting Materials

Pulsed-laser deposition was used to synthesize artificially layered high-temperature superconductors. Thin-film compounds were formed when the constraint of epitaxy was used to stabilize SrCuO(2)-BaCuO(2) superlattices in the infinite layer structure. Using this approach, two new structural families, Ba(2)Srn-1,Cun+1 O2n+2+delta and Ba(4)Srn-1 Cun+3O2n+6+delta have been synthesized; these families superconduct at temperatures as high as 70 kelvin.