摘要:

Superconducting thin films of Y‐Ba‐Cu‐O were fabricated on a CaF2/GaAs(100) substrate using the rf planar magnetron sputtering technique. Substrates were heated as low as 450 °C during deposition. The as‐deposited films without high‐temperature post‐annealing have a transition temperature of 75 K and zero resistance temperature of 45 K. The perovskite structure usually observed in this system was not observed. The critical current (Jc) value of 2×103A/cm2was measured at 4.2 K.

ISSN:0003-6951    

DOI:10.1063/1.101379

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Theory of ac losses in the type II superconductors in the frame of the critical state model [J. Thompson, M. Maley, and J. R. Clem, J. Appl. Phys.50, 3531, 3518 (1979)] is applied to highTcmaterials (Y‐Ba‐Cu‐O) assuming an exponential drop of the critical current densityJcwith both magnetic field and temperature. The dependence of dc magnetic field (H1) at which ac loss minimum occurs on an amplitude of ac magnetic field (h0) and on temperatureTcis calculated numerically. The two maxima of the total ac losses are found: one of them is very close toTcand second maximum belowTcshifts to lower temperatures with increasing ac or dc magnetic field.

ISSN:0003-6951    

DOI:10.1063/1.101454

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The first measurements of the microwave surface resistance at 18 GHz of bulk Tl‐Ba‐Ca‐Cu‐O superconductors produced by the hot isostatic pressing (HIP) process are reported. The superconducting samples, prepared by solid‐state reaction with subsequent sintering and consolidation to obtain ideal density, were measured by replacing the end wall of a TE011circular mode gold‐plated copper cavity with the sample and determining the cavityQfor the temperature range 4–300 K. Results indicated that HIP samples which underwent subsequent annealing exhibit, below the critical temperature, a surface resistance approaching an order of magnitude less than copper.

ISSN:0003-6951    

DOI:10.1063/1.100972

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A highTcsuperconductor of Pb‐doped BiSrCaCuO with aTcof 102 K was prepared. A new phase distinguished from that of undoped BiSrCaCuO was formed by Pb doping. It is reported that the Pb doping, sintering time, and low‐temperature anneal are important to stabilize the highTcphase in BiSrCaCuO. TheJcvalue (77 K,H=0) was measured as 23 A/cm2.

ISSN:0003-6951    

DOI:10.1063/1.101362

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have investigated the magnetic properties of liquid‐quenched Pr15(Fe1−xCox)77B8over the whole range of Co concentrations. The coercivityHciand the remanenceJrdepend on the Co content in the same way as in Nd15(Fe1−xCox)77B8. For the ternary Pr‐Co‐B a highHci, as large as 15.2 kA/cm, has been obtained. In Co‐rich alloys the temperature dependence ofHciandJris limited by the spin reorientation at temperatures well below the Curie point. Except for Pr15Co77B8, annealing of overquenched ribbons leads to substantially lower coercivities. The possible microstructural origin of the magnetic hardening is discussed.

ISSN:0003-6951    

DOI:10.1063/1.101455

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The effects of In doping on crystalline qualities are demonstrated in the heteroepitaxy of GaAs on Si grown by molecular beam epitaxy. The etch pit density of the GaAs layers doped with In at 8×1017cm−3decreased by a factor of 7 compared with undoped GaAs layers. Dark regions observed in electron beam induced current images became small by In doping. The improvement of the crystalline qualities was also verified by Raman spectroscopy.

ISSN:0003-6951    

DOI:10.1063/1.100973

出版商:AIP    

年代:1989

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.100974

出版商:AIP    

年代:1989

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.100975

出版商:AIP    

年代:1989

数据来源: AIP