Huge compact flux avalanches in superconducting Nb thin films

Welling, M. S.; Westerwaal, R.J.; Lohstroh, Wiebke; Wijngaarden, Rinke J.

doi:10.1016/j.physc.2004.06.011

Cited by 44 publications

(61 citation statements)

References 17 publications

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“…A similar effect was previously observed in Nb films. 26 The evolution of the shape of the dendrites in their transverse direction is shown in Fig. 4͑c͒.…”

Section: Dendrite Field Evolutionmentioning

confidence: 99%

Dendritic flux penetration in Pb films with a periodic array of antidots

et al. 2005

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We explore the flux-jump regime in type-II Pb thin films with a periodic array of antidots by means of magneto-optical measurements. A direct visualization of the magnetic flux distribution allows us to identify a rich morphology of flux penetration patterns. We determine the phase boundary H * ͑T͒ between dendritic penetration at low temperatures and a smooth flux invasion at high temperatures and fields. For the whole range of fields and temperatures studied, guided vortex motion along the principal axes of the square pinning array is clearly observed. In particular, the branching process of the dendrite expansion is fully governed by the underlying pinning topology. A comparative study between macroscopic techniques and direct local visualization sheds light onto the puzzling T-and H-independent magnetic response observed at low temperatures and fields. Finally, we find that the distribution of avalanche sizes at low temperatures can be described by a power law with exponent ϳ 0.9͑1͒.

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“…A similar effect was previously observed in Nb films. 26 The evolution of the shape of the dendrites in their transverse direction is shown in Fig. 4͑c͒.…”

Section: Dendrite Field Evolutionmentioning

confidence: 99%

Dendritic flux penetration in Pb films with a periodic array of antidots

et al. 2005

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“…Using magnetooptical imaging [10] the residual flux distribution left in the film after such avalanche events have been observed in many superconducting materials [11][12][13][14]. The experiments also show that there is a threshold magnetic field, H th , for the onset of avalanche activity, and that the unstable behavior is restricted to temperatures below a threshold value, T th , see Fig.…”

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confidence: 99%

Oscillatory regimes of the thermomagnetic instability in superconducting films

2016

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The stability of superconducting films with respect to oscillatory precursor modes for thermomagnetic avalanches is investigated theoretically. The results for the onset threshold show that previous treatments of non-oscillatory modes have predicted much higher thresholds. Thus, in film superconductors, oscillatory modes are far more likely to cause thermomagnetic breakdown. This explains the experimental fact that flux avalanches in film superconductors can occur even at very small ramping rates of the applied magnetic field. Closed expressions for the threshold magnetic field and temperature, as well oscillation frequency, are derived for different regimes of the oscillatory thermomagnetic instability.PACS numbers: 74.25. Ha, 68.60.Dv, The irreversible electromagnetic properties of type-II superconductors are commonly explained in terms of the critical current density j c , as introduced by Bean [1]. In the corresponding critical state the distribution of magnetic flux is nonuniform and metastable. However, since j c is a decreasing function of temperature the metastable state can become unstable driven by the Joule heat generated during flux motion. In bulk superconductors this thermomagnetic instability gives rise to abrupt displacement of large amounts of flux, so-called flux jumps, which may cause the entire superconductor to be heated to the normal state [2][3][4][5][6]. In some cases, pronounced oscillations in magnetization and temperature have been detected prior to such jumps [7,8].In film superconductors experiencing an increasing transverse magnetic fields, the thermomagnetic instability gives rise to abrupt flux entry in the form of dendritic structures rooted at the sample edge [9]. Using magnetooptical imaging [10] the residual flux distribution left in the film after such avalanche events have been observed in many superconducting materials [11][12][13][14]. The experiments also show that there is a threshold magnetic field, H th , for the onset of avalanche activity, and that the unstable behavior is restricted to temperatures below a threshold value, T th , see Fig. 1. These thresholds have been explained on the basis of linear stability analysis of the nonlinear and non-local equations governing the electrodynamics of such films [15][16][17][18][19][20]. The theoretical works show that in order to trigger avalanches an electrical field in the range E = 30-100 mV/m is required.Experimentally, one finds in films of many materials, e.g., MgB 2 , Nb and NbN, that avalanches occur even when the magnetic field is ramped very slowly, e.g., below 1 mT/s [21], inducing correspondingly small E-fields. For a film placed in a magnetic field ramped at a rate of µ 0Ḣa the Bean model estimates [22] the E-field along the edge as E ∼ µ 0Ḣa w, where w is the half-width of the film. With a size of a few millimeters and a ramping rate of 1 mT/s the edge field is E ∼ 1 µV/m, i.e., several orders of magnitude below the theoretical threshold. Hence, thermomagnetic avalanches should not occur at such ramping rates, ...

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“…2,4 Nevertheless, numerous magneto-optical imaging (MOI) studies performed in thin film superconductors made of Nb, 5,6 Nb 3 Sn, 7 NbN, 8 MgB 2 , 9-12 YNiB 2 C, 13 Pb, 14 and YBa 2 Cu 3 O 7Àd , 15,20 placed in a perpendicular dc magnetic field, have revealed that TMI can result in strongly branched dendritic flux patterns. Actually, by using MOI it has been possible to visualize the spatial distribution of the magnetic flux before and after the thermomagnetic breakdown when the magnetic field is ramped (increased or decreased) [5][6][7][8][10][11][12][13][14] or when the flux jump is triggered by pulsed transport currents. 9 Vortex instabilities have been also observed in the microwave (MW) response of MgB 2 resonators as jumps in the resonance curves of the frequency-dependent complex transmission coefficient.…”

Section: Introductionmentioning

confidence: 99%

Avalanche-like vortex penetration driven by pulsed microwave fields in an epitaxial LaSrCuO thin film

Cuadra-Solís

Hernández

García-Santiago

et al. 2013

Journal of Applied Physics

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Different vortex penetration regimes have been registered in the output voltage signal of a magnetometer when single microwave pulses are applied to an epitaxial overdoped La 2Àx Sr x CuO 4 thin film in a perpendicular dc magnetic field. The onset of a significant variation in the sample magnetization which exists below threshold values of temperature, dc magnetic field, and pulse duration is interpreted as an avalanche-type flux penetration. The microwave contribution to the background electric field suggests that the nucleation of this fast vortex motion is of electric origin, which also guarantees the occurrence of vortex instabilities under adiabatic conditions via the enhancement of the flux flow resistivity. Flux creep phenomena and heat transfer effects act as stabilizing factors against the microwave-pulse-induced fast flux diffusion. V C 2013 AIP Publishing LLC. [http://dx

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Huge compact flux avalanches in superconducting Nb thin films

Cited by 44 publications

References 17 publications

Dendritic flux penetration in Pb films with a periodic array of antidots

Dendritic flux penetration in Pb films with a periodic array of antidots

Oscillatory regimes of the thermomagnetic instability in superconducting films

Avalanche-like vortex penetration driven by pulsed microwave fields in an epitaxial LaSrCuO thin film

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