Elimination of magnetic relaxation in superconductors on approaching a ferromagnet

Smolyak, B. M.; Ermakov, G. V.

doi:10.1016/j.physc.2009.12.044

Cited by 6 publications

(4 citation statements)

References 13 publications

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“…To keep the J c constant as per Bean's model, currents of opposite polarities have to be generated and the current structure in the material has to change from being unipolar to bipolar. This can happen in the material when there is a suppression of the magnetic relaxation in the presence of a ferromagnet as a consequence of reversal of polarities [12,13]. It has been suggested in these works that the permanent magnet might also get magnetized to an extent in the presence of the superconductor which in turn induces currents in the superconductor, which circulate in a direction opposite to the original currents.…”

Section: Theory and Modelmentioning

confidence: 99%

Near-oscillatory relaxation behavior of levitation force in infiltration and growth processed bulk YBCO/Ag superconducting composites

Parthasarathy

Lakshmi

Seshubai

2011

Physica C: Superconductivity

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Section: Theory and Modelmentioning

confidence: 99%

Near-oscillatory relaxation behavior of levitation force in infiltration and growth processed bulk YBCO/Ag superconducting composites

Parthasarathy

Lakshmi

Seshubai

2011

Physica C: Superconductivity

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“…One can come to the problem of the creep in another way without touching on the pinning force. In the papers [8,9], the effect of suppression of trapped flux creep in a superconductor when it approaches a ferromagnet was described. It was supposed [8] that a ferromagnet excites the currents in the near-surface region of a sample circulating counter to the trapping current; as a result, the counter Lorentz forces act on vortices in this region that retard the magnetic relaxation.…”

Section: Introductionmentioning

confidence: 99%

“…In the papers [8,9], the effect of suppression of trapped flux creep in a superconductor when it approaches a ferromagnet was described. It was supposed [8] that a ferromagnet excites the currents in the near-surface region of a sample circulating counter to the trapping current; as a result, the counter Lorentz forces act on vortices in this region that retard the magnetic relaxation. It was assumed that the creep can also be suppressed by an external magnetic field having a profile similar to the profile of the ferromagnet's field, and preliminary experiments were performed [9].…”

Section: Introductionmentioning

confidence: 99%

Slowing-down of the vortex motion in the flux creep process by counter forces exerted on the vortex ends

Smolyak

Zakharov

2012

Supercond. Sci. Technol.

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The effect of the suppression of flux creep in a high-temperature superconductor by counter forces exerted on the vortex ends was studied. These forces, acting in the opposite direction to the process of vortex diffusion, arise when the magnetized sample is put into a nonuniform magnetic field. The source of the field should be placed near the surface of the superconductor where the flux line ends are located. The critical states in a disk sample placed near a ferromagnet or permanent magnets were calculated. The results of the calculations verify the bipolar current structure and, therefore, the existence of counter Lorentz forces in the near-surface region. It was shown that in addition to the Lorentz force it is necessary to take into account the magnetic force acting on the vortex ends in the external nonuniform magnetic field. Depending on the direction of this force, the magnetic relaxation slows down or accelerates.

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“…Although the relaxation decay is mostly found to show a logarithmic time dependence [8], any decay may degrade the performance of superconducting magnetic devices, and finally involve potential influences on the operation stability. From this viewpoint, the magnetic relaxation phenomenon has aroused great attention of worldwide researchers and formed a crucial and intense topic accompanying the engineering applications of bulk HTS [8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Relaxation Properties of the Trapped Flux of Bulk High-Temperature Superconductors at Different Magnetization Levels

Deng

Tsuzuki

Miki

et al. 2011

J Supercond Nov Magn

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The magnetic relaxation phenomenon is a crucial subject for the engineering applications of bulk hightemperature superconductors (HTS) in which the trapped field or levitation force behaves with a time-dependent decay due to the intrinsic flux creep inside the HTS materials. To fully exploit the high trapped field of bulk HTS, we have experimentally investigated the trapped flux relaxation properties, especially at different magnetization levels. With different excitation fields, the dependence between trapped field and relaxation rate was analyzed and compared in both field-cooling magnetization (FCM) and zero-fieldcooling magnetization (ZFCM) conditions. In parallel, the relaxation rates for different trapped flux can be measured all at once during a single magnetization process. The relaxation rate is closely correlated to the trapped field and useful to reflect the effect of the following remagnetization processes. To suppress the relaxation, we further checked possible methods from the three aspects of material improvement, working temperature and flux annealing effect.

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Elimination of magnetic relaxation in superconductors on approaching a ferromagnet

Cited by 6 publications

References 13 publications

Near-oscillatory relaxation behavior of levitation force in infiltration and growth processed bulk YBCO/Ag superconducting composites

Near-oscillatory relaxation behavior of levitation force in infiltration and growth processed bulk YBCO/Ag superconducting composites

Slowing-down of the vortex motion in the flux creep process by counter forces exerted on the vortex ends

Relaxation Properties of the Trapped Flux of Bulk High-Temperature Superconductors at Different Magnetization Levels

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