Hysteresis losses and magnetic phenomena in oscillating disks of type II superconductors
Hysteresis losses and the behavior of the magnetic flux threading superconducting disks of Nb oscillating slowly over various angular displacements in static magnetic fields H0 directed perpendicular to the axis of rotation have been investigated by continuously monitoring 〈Bz〉 and 〈By〉, the average...
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Veröffentlicht in: | J. Appl. Phys.; (United States) 1982-03, Vol.53 (3), p.1631-1648 |
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Sprache: | eng |
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Zusammenfassung: | Hysteresis losses and the behavior of the magnetic flux threading superconducting disks of Nb oscillating slowly over various angular displacements in static magnetic fields H0 directed perpendicular to the axis of rotation have been investigated by continuously monitoring 〈Bz〉 and 〈By〉, the average components of the magnetic induction, in the plane of the disk, parallel and perpendicular to H0. A simple model proposed previously satisfactorily accounts for the initial changes, starting from various initial flux configurations, the subsequent cyclical behavior, and the hysteresis losses. Expulsion of flux from the disk occurs during part of the first oscillation, then the amount of flux threading the disk remains constant during the subsequent oscillations, although the orientation distribution of the flux profile undergoes spectacular periodic variations. The analysis shows that dψ/dx = ±k dB/dx describes the orientation of the sheets of flux lines with respect to H0 with distance from the flat surfaces. dB/dx is the critical gradient of flux density and k(T) is the shearing parameter of the flux lattice for the sample. The surface step, ignored in the previous work, is introduced in the model using simple approximations. |
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ISSN: | 0021-8979 1089-7550 |
DOI: | 10.1063/1.330613 |