摘要:

YBa2Cu3O7−x/SrTiO3/Au multilayer systems have been preparedinsituby pulsed laser deposition onto (100) SrTiO3substrates. An electric field controlled device was patterned by suitable metal masks applied successively during the deposition process. The switching time of the superconducting source‐drain channel has been studied atT=4.2 K applying rectangular pulses to the gate electrode. We find that the source‐drain voltage follows the gate voltage variation in accordance with theRCtime constant of the device. Our result is consistent with the mechanism of direct charge transfer by the electric field, but inconsistent with a model based on electric field driven migration of the oxygen atoms in the CuO chains of YBa2Cu3O7−xwhich predicts characteristic times in the order of minutes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115083

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied by Auger electron spectroscopy the incorporation of silver in epitaxial YBa2Cu3O7(YBCO) thin films fabricated by pulsed laser deposition using YBCO+Ag 10% targets. Films were grown on MgO substrates. The silver was found in a thin layer, of approximately 50 nm in depth. X‐ray photoelectron spectroscopy confirmed that the Ag is in its metallic form. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115084

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have fabricated and tested integrated magnetometers based on the superconducting quantum interference device (SQUID). The magnetometer consists of two patterned films of YBa2Cu3O7, separated by an insulating layer of SrTiO3. A multiturn input coil was integrated on top of the SQUID, where the misorientation angle in a SrTiO3bicrystal substrate was used to form the grain boundary junctions. The noise spectrum was characterized at 77 K and showed that above 10 Hz the magnetometer sensitivity is limited by a white noise level of around 4×10−5&Fgr;0/Hz1/2. In the 4 mm × 4 mm detection area of the input coil, this translates into a magnetic field sensitivity of 320 fT/ Hz1/2at 100 Hz. Compared to the theoretical value of an optimized SQUID the white noise level of the magnetometer is two times higher. Below 10 Hz the noise is dominated by 1/fnoise mainly due to the critical current fluctuations. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115085

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Distinct crystalline superconducting grains of Tl2Ba2Ca2Cu3O10+x(Tl−2223) with sizes up to 150 &mgr;m×150 &mgr;m×1 &mgr;m were prepared by a single target dc‐sputtering process followed by proper postannealing at temperatures around 910 °C. A reactive ion etching process was developed to pattern an ∼10 &mgr;m wide bridge with four contact leads directly on a single grain to study its superconducting transport properties. The etching process was found to have only minimal effect on the superconducting transition temperatureTc, which was typically around 110 K. Grains grown on MgO(100) and LaAlO3(100) substrates, although displaying somewhat different in‐plane orientations, all had critical current densitiesJc, well above 106A/cm2at 77 K. The existence of only one grain boundary, however, can reduce theJcby orders of magnitude. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115086

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We describe the noise performance of dc SQUIDs fabricated with quasiplanar ramp‐type Josephson junctions on the basis ofc‐axis‐oriented YBa2Cu3O7/PrBa2Cu3O7thin‐film heterostructures. The noise spectrum of the dc SQUIDs was measured with dc‐ and ac‐bias schemes at different temperatures and showed values below 10−5&Fgr;0/Hz1/2down to frequencies of about 1 Hz at 70 K. Up to now for the magnetic flux noise and the energy resolution obtained at 1 kHz and 77 K the best values were 2.5×10−6, &Fgr;0/Hz1/2and 3×10−31J/Hz, respectively. A study of the white and 1/fnoises of the SQUIDs was performed. The influence of magnetic flux, bias current, high static magnetic fields, and aging on the SQUID noise were investigated. The junctions and devices do not degrade due to aging in air or thermal cycling. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115087

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the synthesis by radio frequency sputtering and characterization of thin films of La0.74Pb0.26MnOzon Si, the substrate of choice for device integration. Textured films with (110) orientation were grown on (100) Si and the films are ferromagnetic below 325 K. Resistivity &rgr; data show a metal‐to‐semiconductor transition atTms=250 K. The ferromagnetic resonance linewidth shows a discontinuity atTms. Data on magnetoresistance MR=[&rgr;(0)−&rgr;(H)]/&rgr;(0) versus temperature indicate a maximum value of 22% atTmsfor a static magnetic field of 2 T and MR values of 15%–22% are observed over the entire temperature range 5–300 K. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115088

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigated the magnetoresistance of La2/3Ca1/3MnO3+&dgr;magnetic thin films. Under certain conditions, the magnetoresistance curves show a remarkable hysteresis and the resistance becomes dependent on the magnetic history. A relaxation behavior of the resistance has also been observed. Hysteresis and relaxation of the resistance are very similar to the phenomena of magnetoviscosity of the magnetic moment in spin glasses and the magnetic aftereffect in hard magnets. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115089

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Universal features ofI–Vcharacteristics of one‐dimensional arrays of normal metal tunnel junctions have been tested against inhomogenities in the junction parameters, number of junctions in the array, and magnetic field. We find that the differential conductance versus bias voltage obeys the analytic form to within 1% if the fabrication errors are smaller than 10% in junction areas, and if the array has more than ten junctions. Furthermore, the universal relation is insensitive to magnetic field at least up to 8 T. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115090

出版商:AIP    

年代:1995

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.115553

出版商:AIP    

年代:1995

数据来源: AIP