摘要:

Detailed measurements have been made of the magnetic field (0<H<6 T) and temperature (10 K<T<100 K) dependencies of the critical current densityjcin Tl2CaBa2Cu2O8films before and after irradiation with incremental fluences (0<&Fgr;<3×1016cm−2) of 2 MeV protons. The results are interpreted quantitatively in terms of radiation‐induced changes in (1) the critical temperature, (2) the rate of thermal flux creep, and (3) local scale superconductivity. Radiation‐induced enhancements injcare described by an expression which allows the fluence that maximizesjcto be predicted as a function ofH,T, pinning energy, and particle type.

ISSN:0003-6951    

DOI:10.1063/1.105915

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have fabricated a YBa2Cu3O7(YBCO) thin‐film dc superconducting quantum interference device (SQUID) with lithographically defined deep‐submicron weak links. At 77 K the voltage response to dc flux is sinusoidal and nonhysteretic, with maximum peak‐to‐peak amplitude of 5 &mgr;V. The maximum response is 8 &mgr;V at 70 K, where 2LI0/&Fgr;0≊1. At lower temperatures, the maximum response oscillates in the range 4–6 &mgr;V. Random telegraph noise was observed near 30–40 K. Well‐behaved Shapiro steps were observable at all measured temperatures belowTc.

ISSN:0003-6951    

DOI:10.1063/1.105916

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have used laser deposition to make YBa2Cu3O7−&dgr;/NdGaO3/YBa2Cu3O7−&dgr;trilayer structures. NdGaO3films grow epitaxially on well lattice‐matched substrates, like SrTiO3(100), and onc‐axis oriented YBa2Cu3O7−&dgr;films. Epitaxial YBa2Cu3O7−&dgr;films were grown on top of the NdGaO3films, and there was no significant difference in critical temperature between top and bottom layers of the trilayer structures. The resistivity of a 300‐nm‐thick NdGaO3interlayer was as high as 108&OHgr; cm at 300 K.

ISSN:0003-6951    

DOI:10.1063/1.105917

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have demonstrated a new planarized all‐refractory technology for lowTcsuperconductivity (PARTS). With the exception of the Nb‐AlOx‐Nb trilayer preparation, the processing is done almost exclusively within an advanced Si technology fabrication facility. This approach has allowed us to leverage highly off of existing state‐of‐the‐art lithography, metal etching, materials deposition, and planarization capabilities. Using chemical‐mechanical polish as the planarization technique we have fabricated Josephson junctions ranging in size from 0.5–100 &mgr;m2. Junction quality is excellent with the figure of meritVmtypically exceeding 70 mV. PARTS has yielded fully functional integrated Josephson devices including magnetometers, gradiometers, and soliton oscillators.

ISSN:0003-6951    

DOI:10.1063/1.106405

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We investigated the stabilization of magnetic flux in a high‐temperature superconductor (a proton‐irradiated Y1Ba2Cu3O7crystal), by operating with subcritical current densityJ. Using the thermal history to obtain an induced current densityJ≤Jc, we observed a drastically reduced relaxation ratedM/dt(M=magnetization), after ‘‘flux creep annealing.’’ The results show that the field gradient ∼J∼Mdetermined the relaxation rate, independent of the sample’sH‐Thistory, in agreement with recent theory.

ISSN:0003-6951    

DOI:10.1063/1.105918

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Data are presented which indicate that a very simple technique for enhancing the critical current in flat, coreless superconductor cables is to match the cable twist pitch with the strand twist pitch in such a way that the same group of filaments within each strand is degraded at each successive bend at the cable edges. This coincidence condition minimizes current transfer among filaments, enhances the slope of the voltage‐current characteristic, consistently improves the critical current by about 10% in these tests, and is easy to apply.

ISSN:0003-6951    

DOI:10.1063/1.105919

出版商:AIP    

年代:1991

数据来源: AIP