The response of pinned flux vortices to low-frequency fields

Campbell, A.M.

doi:10.1088/0022-3719/2/8/318

Cited by 353 publications

(141 citation statements)

References 12 publications

Supporting

Mentioning

134

Contrasting

Unclassified

Order By: Relevance

“…While the distribution of pinning centres in the bulk is almost homogeneous, there is a highly inhomogeneous surface layer of about 8 m in which the critical current density increases to about 25 times the value in the bulk. This effect, which has been reported for various types of samples [4,17,24,251, is ascribed to a higher concentration of deformations and impurities near the surface. It can be seen from fig.…”

Section: Resultssupporting

confidence: 63%

The response of type H superconductors to trapezoidal magnetic fields

1978

View full text Add to dashboard Cite

The inductive response of type I1 superconductors to applied fields with trapezoidal time dependence is described for samples with a slab geometry. An extension of the critical state model which accounts for the observed waveform of the voltage, induced in the pick-up coil, is given. Typical experiments on Nb-slabs with weak pinning and flux flow in fields with both small and large amplitudes are reported.

show abstract

Section: Resultssupporting

confidence: 63%

The response of type H superconductors to trapezoidal magnetic fields

1978

View full text Add to dashboard Cite

show abstract

“…At low frequencies, say f 1 KHz, a small ac field has an apparent penetration characterized by a static regime without any loss (the Campbell regime). It has been recognized as a direct consequence of the vortex pinning, and disagrees with first interpretations based on thermally activated depinning [2]. Note that this linear regime is not the ohmic regime of a vortex lattice free from any pinning (the so called liquid phase).…”

contrasting

confidence: 62%

The vortex depinning transition in untwined YBaCuO using complex impedance measurements

Pautrat¹,

Goupil²,

Simon³

et al. 2004

Physica C: Superconductivity

View full text Add to dashboard Cite

We present surface impedance measurement of the vortex linear response in a large untwinned YBCO crystal. The depinning spectra obtained over a broad frequency range (100 Hz-30 MHz) are those of a surface pinned vortex lattice with a free flux flow resistivity (two modes response). The critical current in the "Campbell" like regime and the flux flow resistivity in the dissipative regime are extracted. Those two parameters are affected by the first order transition, showing that this transition may be related to the electronic state of vortices.The linear ac response of a pinned vortex lattice has been observed in the 60's in conventional type II superconducting materials [1]. At low frequencies, say f 1 KHz, a small ac field has an apparent penetration characterized by a static regime without any loss (the Campbell regime). It has been recognized as a direct consequence of the vortex pinning, and disagrees with first interpretations based on thermally activated depinning [2]. Note that this linear regime is not the ohmic regime of a vortex lattice free from any pinning (the so called liquid phase). At the same time, the high frequency response (f 1-10 MHz) is that of a medium with a free resistivity (skin effect). Those two regimes are separated by the depinning frequency, and the shape of the whole spectrum allows to discriminate between different types of pinned vortex states. One of the main interest of this method is that vortex states can be studied even in the presence of a large critical current. The principle of the experiment is to measure the ac penetration length, due to the vortex response, in a small coil directly glued around the sample. The detailed experimental procedure can be found in [3]. A typical depinning spectrum is shown in the figure 1. It follows closely, over the whole frequency range, the two modes model of

show abstract

“…It is also worth mentioning that, by taking α p , α v = 0, one recovers the single-species models, in which the whole dynamics is described in terms of a single elastic constant. Accordingly, in the low-frequency limit considered here one would have the well known Campbell response, 36 µ v (ω) = φ 0 /α r (ω), but with a dispersive, complex Labusch constant, given by Eq. (13), accounting for linear flux creep.…”

Section: B Response Function Of a Nanostructured Superconducting Stripmentioning

confidence: 99%

Probing the low-frequency vortex dynamics in a nanostructured superconducting strip

et al. 2016

View full text Add to dashboard Cite

We investigate by scanning susceptibility microscopy the response of a thin Pb strip, with a square array of submicron antidots, to a low-frequency ac magnetic field applied perpendicularly to the film plane. By mapping the local permeability of the sample within the field range where vortices trapped by the antidots and interstitial vortices coexist, we observed two distinct dynamical regimes occurring at different temperatures. At a temperature just below the superconducting transition, T /Tc = 0.96, the sample response is essentially dominated by the motion of highly mobile interstitial vortices. However, at a slightly lower temperature, T /Tc = 0.93, the interstitial vortices freeze up leading to a strong reduction of the ac screening length. We propose a simple model for the vortex response in this system which fits well to the experimental data. Our analysis suggests that the observed switching to the high mobility regime stems from a resonant effect, where the period of the ac excitation is just large enough to allow interstitial vortices to thermally hop through the weak pinning landscape produced by random material defects. This argument is further supported by the observation of a pronounced enhancement of the out-of-phase response at the crossover between both dynamical regimes.

show abstract

The response of pinned flux vortices to low-frequency fields

Cited by 353 publications

References 12 publications

The response of type H superconductors to trapezoidal magnetic fields

The response of type H superconductors to trapezoidal magnetic fields

The vortex depinning transition in untwined YBaCuO using complex impedance measurements

Probing the low-frequency vortex dynamics in a nanostructured superconducting strip

Contact Info

Product

Resources

About