摘要:

Highlyc‐axis‐oriented Tl2Ba2Ca2Cu3Oxsuperconducting thin films with the critical current density as high as 1×107A/cm2at 87 K were obtained by single‐target dc sputtering on LaAlO3(100) substrates followed by encapsulated compensate annealing. The strong linear temperature dependence of zero‐field critical current at low temperatures suggests a creep‐dominated behavior. Preliminary field dependence studies on the critical current density in low‐field regime (<2 kOe) shows no evidence of hysteresis commonly encountered in films with higher granularity. The scaling behavior of the global pinning force density exhibits strong resemblance to conventional type‐II superconductors with the pinning force density of the same order of magnitude as that in strong pinned NbN thin films.

ISSN:0003-6951    

DOI:10.1063/1.106364

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have developed aninsituprocess for fabricating high transition temperature superconductor‐normal metal‐superconductor microbridges using a step edge to define the normal metal length. Critical current‐normal resistance products over 1 mV have been measured at low temperature in devices with high‐resistivity Ag‐Au alloy bridges. Results on samples with Ag bridges are compared with the alloy data as an initial test of recent theories of SNS Josephson junctions. Josephson effects have been demonstrated in these devices at temperatures higher than 80 K. Clearly defined rf steps have been observed, with power dependence qualitatively similar to theoretical predictions.

ISSN:0003-6951    

DOI:10.1063/1.106365

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A study of the dependence of the transport critical current density (Jc) on the width of Y1Ba2Cu3O7thin‐film microbridges with widths down to 2 &mgr;m has been made. No evidence of edge pinning, which leads to largerJc’s in narrower microbridges, was found. Due to the limitation in resolution of photolithography encountered in common usage, a tapered or radiation damaged edge was always present, which may have introduced a significant error in the cross section and hence in the estimation ofJc. By normalizing the critical current (Ic) to the room‐temperature resistance of the microbridge, we can eliminate this mask‐defined cross‐sectional error.

ISSN:0003-6951    

DOI:10.1063/1.106366

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A study of drag in rotating permanent magnet/high temperature superconductor magnetic bearings is reported. The effects of magnet asymmetry, atmospheric resistance, and eddy currents are discussed. One of the bearings achieved a rotational speed of 200 000 RPM and a low speed coefficient of friction of 8.1×10−6, values that have technological significance for flywheel energy storage.

ISSN:0003-6951    

DOI:10.1063/1.106367

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.106424

出版商:AIP    

年代:1991

数据来源: AIP