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Titolo:
Vortex dynamics of Nb variable-thickness bridges measured by direct flux detection method
Autore:
Hirano, S; Hirata, Y; Kuriki, S; Matsuda, M; Morooka, T; Nakayama, S;
Indirizzi:
Hokkaido Univ, Res Inst Elect Sci, Sapporo, Hokkaido 0600812, Japan Hokkaido Univ Sapporo Hokkaido Japan 0600812 oro, Hokkaido 0600812, Japan Muroran Inst Technol, Muroran, Hokkaido 0508585, Japan Muroran Inst Technol Muroran Hokkaido Japan 0508585 kkaido 0508585, Japan Seiko Instruments Inc, Chiba 2702222, Japan Seiko Instruments Inc Chiba Japan 2702222 ents Inc, Chiba 2702222, Japan
Titolo Testata:
JOURNAL OF APPLIED PHYSICS
fascicolo: 11, volume: 85, anno: 1999,
pagine: 7819 - 7823
SICI:
0021-8979(19990601)85:11<7819:VDONVB>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
FLOW NOISE; SUPERCONDUCTORS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
--discip_EC--
Citazioni:
11
Recensione:
Indirizzi per estratti:
Indirizzo: Hirano, S Hokkaido Univ, Res Inst Elect Sci, Sapporo, Hokkaido 0600812, Japan Hokkaido Univ Sapporo Hokkaido Japan 0600812 ido 0600812, Japan
Citazione:
S. Hirano et al., "Vortex dynamics of Nb variable-thickness bridges measured by direct flux detection method", J APPL PHYS, 85(11), 1999, pp. 7819-7823

Abstract

In order to study the dynamical behavior of vortices moving through superconducting thin film devices, we constructed a probe having a concentric thin-film planar gradiometer coupled to a direct current SQUID. The probe was designed to directly detect the flux generated by a single vortex, based onthe monopole approximation. Measurements of static current-voltage (I-V) and flux noise characteristics were made for variable-thickness bridges (VTB) made on epitaxial Nb films. The critical current was unambiguously determined from the onset of vortex motion. Multiple step noise of the flux with a minimum step height of 0.28 Phi(0) was observed above the critical current in the time traces. This step height is in agreement with the numerical calculation for single vortex motion, confirming the validity of the monopole approximation. It is suggested that the multiple step noise is generated by the successive entry of single vortices into the bridge. VTBs made on polycrystalline Nb films were also measured. The I-V characteristic showed asymmetric voltage increases and a multiple peak structure of the flux noise was observed above the critical current, suggesting the successive depinning of trapped vortices as flux bundles from widely distributed pinning potentials. (C) 1999 American Institute of Physics. [S0021-8979(99)04611-3].

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Documento generato il 04/04/20 alle ore 08:20:03