摘要:

By manipulating the cooling rate from the final heat treatment, we have raised the 77 K, self‐field critical current density (Jc) of multifilament (Bi,Pb)2Sr2Ca2Cu3Ox(2223) tapes by a factor of 3, and the irreversibility field (H*) by more than 50%. TheJcof samples cooled in 7.5% O2from their reaction temperature of 825 °C increased from ∼8 to ∼24 kA/cm2andH*(77 K) increased from ∼120 to ∼200 mT as the cooling rate was decreased from 5 to 0.016 °C/min. The results unambiguously show that the flux pinning properties of 2223 tapes can be improved by simple changes in wire processing. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117322

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have fabricated YBa2Cu3O7−&dgr;/PrBa2Cu3O7−&dgr;/YBa2Cu3O7−&dgr;ramp‐type Josephson junctions with high characteristic voltageVc=IcRnat a temperature of 77 K. A microshadow mask technique was used to grow completelyinsitua ramp‐type multilayer structure. Junctions with barrier thicknesses of about 13 and 45 nm were characterized. Junctions with a thicker barrier exhibited supercurrent up to 80 K and showed a resistively shunted‐junction‐like current voltage characteristics with aVcas high as ∼1.5 mV at 77 K and 16 mV at 15 K. Junctions with a thinner barrier worked up to 90 K and exhibited the ac Josephson effect at 77 K under 8.9 GHz microwave radiation. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117323

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have fabricated coplanar type dc SQUIDs using NdBa2Cu3Oysuperconducting thin films and operated fundamental single‐flux‐quantum (SFQ) circuits. The Josephson junctions were made by the narrow‐focused ion beam irradiation technique. For a 145 &mgr;m wide and 10 &mgr;m long logic SQUID having a critical current of 105 &mgr;A and an inductive parameter (&bgr;L) of 28, a store and a restore of the flux quantum have been demonstrated at temperatures of 4.2–30 K. These operations were performed with an input pulsewidth of 5 ns (5 ns was the shortest input pulse width available from our function generating equipment). These results show experimentally the possibility of high speed operation in all high‐Tcsuperconducting digital circuits. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117324

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A microscopic chemical analysis of BiSrCaCuO (BSCCO) 2212 single crystals was performed with an unprecedented combination of high (submicron) lateral resolution and high energy resolution (100 meV or better). These performances, achieved with imaging synchrotron spectromicroscopy, enabled us to detect in a very small fraction of the investigated specimens, morphological and chemical inhomogeneities. Specifically, we found deviations from stoichiometry in the surface Sr content which have a subtle effect on the chemical environment of at least one other element, Ca. The different chemical environment was found to influence surface chemical reactions. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117325

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The domain size and the ac‐hysteresis of NiZn‐ferrites have been investigated as a function of grain size. It is found that the ac‐hysteresis or energy dissipation at MHz frequencies is substantially reduced in fine‐grained, monodomain NiZn‐ferrites, which is attributed to the absence of intragranular domain walls. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117326

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The principles of operation of a microelectromechanical (MEMS)‐based magnetometer designed on the magnetoelastic effect are described. The active transduction element is a commercial (001) silicon microcantilever coated with an amorphous thin film of the giant magnetostrictive alloy Terfenol‐D [(Dy0.7Te0.3)Fe2]. In addition to the magnetostrictive transducer, basic components of the magnetometer include: (a) mechanical resonance of the coated‐microcantilever through coupling to an ac magnetic field; and (b) detection by optical beam deflection of the microcantilever motion utilizing a laser diode source and a position‐sensitive detector. Currently, the sensitivity of this MEMS‐based magnetostrictive magnetometer is ∼1&mgr;T. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117327

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

By incorporating iodine gas during the films’ deposition, amorphous diamondlike carbon (a:DLC) films were doped anda:I–DLC films were obtained. Optical measurements showed that iodine affects the optical band gap, decrease it from 1.1 to 0.78 eV. Iodine doping decreased the resistivity by four orders of magnitude, from 108to 104&OHgr; cm. Iodine doped film was found to have a largerpdoping thana:DLC films. TheI–Vcharacteristics of devices made of doped and undoped films grown on silicon substrates, were studied. ac measurements of these devices have shown that thepdopeda:DLC films behave as semiconductors, and give a rectification withn‐type silicon. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117328

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We investigate the nonlinear characteristics of space‐charge waves, which propagate along a relativistic electron beam drifting near the surface of a semi‐infinite Kerr‐like medium, under the condition that the drift velocity of the electron beam does not exceed the Cherenkov threshold. On the basis of the linear fluid model for the electron beam and the stationary wave analysis, we obtain some interesting features for the nonlinear space‐charge waves such as power dependence of wave numbers and hysteresis characteristics. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117329

出版商:AIP    

年代:1996

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.117330

出版商:AIP    

年代:1996

数据来源: AIP