摘要:

We present experimental results for microwave intermodulation in a series of superconducting hairpin resonators. We find that geometry plays a dominant role in determining both the losses and intermodulation in these resonators. The experimental data can be reproduced using recent theoretical calculations with a single parameter,JIMD (77 K). We compare the response of the fundamental and the first harmonic modes of these resonators to find that the use of the first harmonic mode gives less intermodulation, but we also find higher losses due to the more extended fields of this mode. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120537

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present an experimental study of the time scales for various quasiparticle processes in a superconducting single photon spectrometer. Processes studied include quasiparticle recombination, diffusion, trapping, tunneling, and energy redistribution. Experiments were performed with a double junction, imaging x-ray detector whose charge output provides a measure of the photon energy. Time scales are extracted with a simple model and the values of several parameters, including the diffusion constant and recombination time, are found to differ from theoretical predictions. These results provide guidelines for performance analysis, device scaling, and future designs. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120538

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The nonlinear microwave response of superconducting YBa2Cu3O7−&dgr;thin films and crystals was studied quantitatively by measuring the third-order harmonic amplitudeE3&ohgr;(&ohgr;: 35 GHz,jRF⩽3×104A/cm2). We findE3&ohgr;to be dominated by twoextrinsiceffects: (1) the interaction with flux lines in weak links, leading to an increased nonlinear response at low temperatures, and (2) rf related flux line creation at film edges, yielding a highE3&ohgr;-signal close toTc.Both effects together lead to a minimum inE3&ohgr;around 40–60 K, which makes this temperature interval interesting for rf applications. Intrinsic nonlinearities are smaller by orders of magnitude and could not be detected. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120539

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The Mn site substitutions of charge ordered (CO) manganitesLn0.5Ca0.5MnO3(Ln=La–Tb)have been investigated. Among the different studied doping elements, chromium is shown to be the most efficient one to induce a metal insulator (MI) transition in the CO undoped insulators. A newTm(⟨rA⟩)magnetic diagram, where⟨rA⟩is theAsite cationic average radius, is established for the oxidesLn0.5Ca0.5Mn1−xCrxO3,which demonstrates that⟨rA⟩is not a rhedibitory parameter for the occurrence of colossal magnetoresistance (CMR) properties. The average size limit⟨rA⟩L≈1.19 Åbelow which the MI transition is suppressed in the undoped CO compounds is indeed lowered to⟨rA⟩L≈1.14 Åin the Cr-doped materials. The electron microscopy study of these Cr doped oxides shows that this spectacular effect corresponds with the disappearance of the structural transition associated with CO. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120540

出版商:AIP    

年代:1997

数据来源: AIP