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The incorporation of the gold nanorods in Gd[Ba.sub.2][Cu.sub.3][O.sub.7-[delta]] (GdBCO) thin films to enable vortex pinning is described. The results show that the matching effect between the vortices and the gold nanorods leads to the peak effect in them.

The study describes the optimum deposition conditions required for the fabrication of thick Y[Ba.sub.2][Cu.sub.3][O.sub.7-x] (YBCO) films on optimized SrTi[O.sub.3] (STO) buffered-MgO single crystals.

The relationship between in-plane orientation, grain axis fluctuation and critical current, and surface resistance of YBa2Cu3O7-delta films.

In-plane alignment of C-axis oriented thin films was studied to determine the effect of lattice matching.

Research is presented describing the study and development of an efficient high temperature superconducting cooling system for use with miniaturized antennas.

A study on how the microwave surface resistance of YBa2u3Oy (YBCO) thin films are affected by the crystallinity and surface roughness of CeO2 buffer on R-plane Al2O3 substrate was conducted. X-ray diffraction method was used to measure the microwave surface resistance from the microstrip line resonator's transmission characteristics. Results show that the quality of the upper layer of the YBCO is affected by the poor crystallinity of thin CeO2.

The a-axis oriented YBa2Cu3O7 thin films were grown on SrLaGaO4 (100) substrate with a buffer layer of 50 nm thick Gd2CuO4 using pulsed laser deposition technique. The thickness of Y-123 thin film was about 500 nm. Intrinsic Josephson junctions (CuO2 planes) were aligned perpendicular to the substrate in the thin films. The bridge type pattern was fabricated using focused ion beam milling technique in such a way so that the current flow along the c-axis in thin film. The dimensions of bridge were 1 \mum in length along the c-axis and 5 \mum in width along the b-axis. The resistance vs. temperature characteristics showed transition temperature of about 89 K. The critical current density (Jc) of 2\times 10^6\ A/cm^2 was measured from current-voltage (I-V) characteristics at 10 K. The samples were irradiated with external microwave at 20 GHz and the Jc was suppressed with increase in power. This suppression in Jc indicates the formation of layered structure with strong coupling. The voltage steps were appeared with microwave irradiation in I-V characteristics. The values of voltage steps were irregular and change with increase in power. We have also studied all a-axis oriented multilayered thin films of YBa2Cu3O7 (Y123) and PrBa2Cu3O7 (Pr123). We fabricated a submicron stack in which Josephson junctions were forming by Y123 and Pr123. The submicron stack showed response with microwave irradiation of different frequency and power. The transport characteristics of these thin films are discussed in detail. [ABSTRACT FROM AUTHOR]

Influence of growth temperatures are discussed for microstructures and superconducting properties of ErBa2Cu3O7-δ films with Ba(Er0.5Nb0.5)O3 nanorods grown by pulse laser deposition on SrTiO3 substrates. The nanorods were observed in transmission electron microscopy images of the films. Nanorods were thinner and denser at a lower growth temperature. The Jc performance in magnetic fields relates closely the morphology of introduced nanorods with growth temperature. [ABSTRACT FROM AUTHOR]

Gold nanorods were introduced into GdBa2Cu3O7-δ (GdBCO) thin films to form artificial pinning centers. The incorporation of gold nanorods into the GdBCO films was achieved simply by attaching gold sheets to a GdBCO target in the pulsed laser deposition process. Transmission electron microscopy observation showed that gold nanorods grew parallel to the c-axis of the GdBCO films. Small angle X-ray scattering and scanning electron microscopy results indicated that matching field, Bɸ was increased with the amount of supplied gold. Jc – B characteristics in the field aligned with the c-axis at 50 and 65 K exhibited an anomalous shoulder (‘peak effect’) around at Bɸ, and the peak position was not dependent on the temperature. This suggests that the ‘peak effect’ was originated from the matching effect between vortices and the gold nanorods. [ABSTRACT FROM AUTHOR]

In this work, we studied the optimum deposition conditions for SrTiO3 (STO) buffers deposited on MgO single crystals substrates by PLD method. We found that 120 nm thick STO films, deposited at 730 °C, present the smoothest surface and a minimum FWMH of the (002) reflection. High quality, smooth and free-crack YBa2Cu3O7-x (YBCO) thick superconducting films have then been fabricated using a deposition temperature of 800 °C on STO-buffered MgO substrates. A 373 nm thick YBCO/STO/MgO film can carry current densities Jc (77 K, 0 T) of 1.4 MA/cm2 and Jc (77K, 5 T) of 0.14 MA/cm2. The Jc in high field overcomes the current transported in same experimental conditions by 180 nm thick YBCO film grown on Y2O3-decorated STO single crystal. For 1350 nm thick YBCO/STO/MgO film the Jc (77 K, 0 T) is about 0.8 MA/cm2 and Jc (77 K, 5 T) is 0.09 MA/cm2. [ABSTRACT FROM AUTHOR]

A novel technology to introduce artificial pinning centers (APCs) into YBa2 Cu3 O7-δ (YBCO) thin films prepared by pulsed laser deposition (PLD) was investigated for a drastic improvement of Jc in the films. Linear-like defects (one-dimensional APCs) were introduced perpendicular to the surface of the c-axis oriented films during the deposition process by using distributed Y2O3 nano-islands on substrates. The density of nano-islands was varied within 0.8 — 1.2 × 1010 /cm² by PLD. A normalized resistivity as a function of temperature in magnetic fields shows a sharper resistivity drop for the film with APC, compared to pure YBCO film. Jc of the film with APC was also increased to 0.12 MA/cm² (77 K, B//c, 5 T), which was about two times higher than that of the pure YBCO film. The film had a very large Jc peak when the field was applied close to the c-axis. The peak Jc increased with the number density of Y2O3 nano-islands. This indicates that strong APCs parallel to the c-axis were incorporated into the YBCO film. [ABSTRACT FROM AUTHOR]

A c-axis oriented epitaxial REBa2Cu3Oy (RE 123) thin film performs excellent superconducting properties in magnetic field. Recently, we reported that a critical current density (Jc) in the RE123 thin film was improved by a deliberate composition control. A Sm1+xBa2-xCu3Oy (Sm123) thin film with a small amount of Sm/Ba substitution x showed the great Jc ∼ 0.17 MA/cm² in 5 T at 77.3 K, while the Jc in (Yb1-xNdx)Ba2Cu3Oy (Yb/Nd123) thin films depended on an amount of mixed crystal ratio z. In this report, we studied Jc as a function of magnetic field and field orientation with respect to a b-planes. In low magnetic field, the Jc of Sm123 thin film was almost independent of the applied angle of the field. In the case of Yb/Nd 123 thin film, extremely high Jc were observed when the magnetic field was aligned parallel or perpendicular to the surface of the film. Because compositional fluctuations in RE 123 thin films were observed by transmission electron microscopy, we found that the pinning centers in RE 123 thin films are strongly affected by the composition in the thin films. [ABSTRACT FROM AUTHOR]

We investigated the behavior of the surface resistance (Rs) of high-temperature superconductor (HTS) thin films exposed to a dc magnetic field (parallel to the c-axis). Measurements were done using the dielectric resonator method and superconducting magnet system. The DyBa2Cu3O7-δ (DyBCO) and YBa2Cu3O7-δ (YRCO) thin films (produced by THEVA GmbH) were prepared through a thermal co-evaporation method. The resonant frequency of the TE011 mode in the resonator was approximately 22 GHz. A dc magnetic field of up to 5 T was applied vertically to two parallel superconducting thin films placed into a closed-type Cu cavity. Rs of the DyBCO and YBCO thin films increased as the applied dc magnetic field increased. The Rs ratio (defined as Rs(5 T)/Rs(0 T)) of the DyBCO and YBCO thin films at 4.5 K was approximately 5 and 50, respectively. These results indicate that the DyBCO thin film may be better for use in low-temperature nuclear magnetic resonance applications. [ABSTRACT FROM AUTHOR]

We investigated the relationship between the surface resistance (Rs) and critical current density (Jc) of DyBa2Cu3O7-δ (DyBCO) thin films in a dc magnetic field. The Rs of DyBCO films at 21.8 GHz was measured using a dielectric resonator method and the Jc was determined by magnetic measurement and Bean's model. A dc magnetic field of up to 5 T was applied along the c-axis of the films. The relationship between the Rs and Jc of DyBCO thin films under a zero magnetic field was explained by the following equation, Rs = α × 107 /Jc, where α is a constant of 1.2, and the units of the Rs and Jc are ohm and A/m², respectively. In addition, the Rs in dc magnetic fields up to 5 T were inversely proportional to the Jc. However, the parameter α, which was fitted from the Rs — Jc, characteristics in each magnetic field, increased slightly with an increase the magnitude of the applied field. These results indicate that the relationship between the Rs and Jc in a zero magnetic field may be a general property of HTS thin films and that the a in DyBCO thin films depends on the magnitude of the applied magnetic field. [ABSTRACT FROM AUTHOR]

We examined the hetero-epitaxial growth of YBCO thin films on the a-cut plane sapphire substrates for the passive microwave applications, because the a-cut plane sapphire substrates have smaller in-plane anisotropy of the dielectric constant compared with that of r-cut plane sapphire substrates. The CeO2 buffer layers and YBCO thin films were prepared by an inductive-coupled plasma sputtering method. We found that perfect in-plane alignment of the CeO2 buffer layer could be obtained on the a-cut plane sapphire substrates. Also we could obtain the hetero-epitaxial YBCO thin films on CeO2 /a-cut plane sapphire substrates. Tc of the YBCO thin films was approximately 89 K, and the surface resistance (Rs) of the YRCO thin films was approximately 1 mΩ at 50 K and at 22 GHz, equivalently to values for YRCO thin films fabricated on the r-cut plane sapphire substrates. [ABSTRACT FROM AUTHOR]

We developed a novel nondestructive and contactless method for measurements of critical current density (Jc) in high- temperature superconductor (HTS) thin flints by using a permanent magnet (Sm2Co17). This measurement technique is based on a repulsive force (Fr) and attractive force (Fa) between the magnet and HTS film caused by the shielding currents and pinning forces. The Fr and Fa were measured by using a high-resolution load sensor changing the distance (L) between the magnet and HTS film. An effective maximum repulsive force (Fm,eff) could be determined from an extrapolated value of the Fr vs. L curve for L = 0 mm. We investigated the relationship of the Jc to the Fm,eff in many HTS (YBa2Cu3 and ErBa2Cu3 O7-δ) samples. The standard Jc of HTS films was measured by using an inductive measurement system produced from THEVA GmbH. We found that the Jc is almost proportional to the two-thirds power of the Fm,eff normalized by the film thickness. This result indicates that the simple permanent magnet technique can be easily estimate the Jc of the HTS films. This system has good reproducibility for the Jc measurements and is useful to provide a rapid, routine characterization of the superconductivity in the HTS materials. [ABSTRACT FROM AUTHOR]