Dual stage resistive transition of MgB2 evidenced by noise analysis

Tipo di pubblicazione: Articolo su rivista
Tipologia MIUR: Contributo su Rivista > Articolo in rivista
Titolo: Dual stage resistive transition of MgB2 evidenced by noise analysis
Autori: Andreoli V.; Carbone A.; Mazzetti P.; Gandini C.; Masoero E.; Monticone E.
Autori di ateneo:
Titolo del periodico: JOURNAL OF APPLIED PHYSICS
Tipo di referee: Tipo non specificato
Editore: AIP
Volume: 110
Intervallo pagine: 013909-1-013909-7
Numero di pagine: 7
ISSN: 0021-8979
Abstract: The resistive transition of polycrystalline superconducting MgB2 films is studied by means of an extensive set of stationary noise measurements, going from the very beginning of the transition to its final point, where the normal state is reached, either with and without magnetic field. The experimental results, taken at low current density and close to the critical temperature Tc, show very clearly the existence of two different dissipative processes at the different stages of the transition. An extended analysis proves that, at the beginning of the transition, when the resistance is below ten percent of normal value, the specimen is in a mixed state and dissipation is produced by fluxoid creation and motion. At higher temperature the specimen is in an intermediate state, constituted by a structure of interleaved superconducting and resistive domains. Such a situation occurs in type II superconductor when the transition temperature is very near to Tc and the critical field Hc for fluxoid penetration tends to zero. It is found that in the intermediate state, the power spectrum of the relative resistance fluctuations, is independent of the average resistance value and is unaffected by the magnetic field. As shown in the paper, this means that the noise is generated by density fluctuation of the normal electron gas in the resistive domains, while the contribution of the superconducting ones is negligible. The reduced noise amplitude does not depend on the steepness of the transition curve, thus adding further evidence to the above interpretation. The noise is thus related to the film impurities and can be investigated when the specimen is in the normal state, even at room temperature. The occurrence of a different dissipative process at low resistance is clearly evidenced by the experimental results, which show that the amplitude of the reduced power spectrum of the noise depends on magnetic field and resistance. These results are consistent with the assumption of fluxoid noise as shown by the model for the calculation of the noise developed in the manuscript
Data: 2011
Status: Pubblicato
Lingua della pubblicazione: Inglese
Parole chiave:
Dipartimenti (originale): DIFIS - Fisica
Dipartimenti: DISAT - Dipartimento Scienza Applicata e Tecnologia
URL correlate:
    Area disciplinare: Area 02 - Scienze fisiche > FISICA DELLA MATERIA
    Data di deposito: 12 Feb 2012 19:30
    Data ultima modifica (IRIS): 19 Apr 2016 10:25:16
    Data inserimento (PORTO): 04 Feb 2017 23:22
    Numero Identificativo (DOI): 10.1063/1.3605533
    Permalink: http://porto.polito.it/id/eprint/2488906
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