Critical-state model for the determination of critical currents in disk-shaped superconductors

Frankel, D.

doi:10.1063/1.326642

Cited by 174 publications

(47 citation statements)

References 12 publications

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“…There are two factors reducing the PM response for the samples with increased thickness: (1) characteristic scale of a screened field H scr is j c d [34], implying the need of higher J PM c to compensate increased J Sh c , and (2) thick films require more energy to resettle the pinned fluxes towards the center. These thickness tendencies are consistent with the magnetization behavior observed for thin superconducting films in orthogonal magnetic fields [31][32][33][34].…”

Section: Behavior Of Pme Under Different Conditionssupporting

confidence: 85%

“…This value is more than one order smaller than j c obtained directly from transport measurements, j c = j 0K c (1 − T /T c ) ≈ 2 × 10 7 A/m 2 , where j 0K c = 6 × 10 7 A/m 2 (see Table 1). A possible source of the difference is a contribution to the azimuthal critical current from a gradient of the radial field along the axial direction z, ∂H r /∂z [31][32][33][34].…”

Section: Behavior Of Pme Under Different Conditionsmentioning

confidence: 99%

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Paramagnetic Meissner Effect in Electrochemically Doped Indium-Tin Oxide Films

Aliev

Andrade

Salamon

2016

J Supercond Nov Magn

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Transparent conductive indium-tin oxide (ITO) thin films, electrochemically intercalated with alkali (Li + , Na + , K + , Rb + , Cs + ), alkali earth (Mg +2 , Ca +2 ), or complex NH + 4 ions, show tunable superconducting transitions with dome-shaped behavior of T c versus electron density around the maximum at ∼ 5 K. On field cooling, the transition into the superconducting state is accompanied by a paramagnetic response, i.e., an increase of magnetization, rather than the usual diamagnetic Meissner response. We provide an extensive study of this so-called paramagnetic Meissner effect (PME), using DC SQUID, transport measurements and a variety of sample sizes and growth conditions. We show that the PME in electrochemically doped ITO films results from a higher T c at the sample edges than at the center of disk-shaped samples, causing flux to be expelled towards the center of the disk, following the flux-compression theory of Koshelev and Larkin. Changing to the opposite spatial T c profile largely removes the paramagnetic response. The paramagnetic magnetization is strongly influenced by sample geometry and flux pinning Electronic supplementary material The online version of this article (

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Section: Behavior Of Pme Under Different Conditionssupporting

confidence: 85%

Section: Behavior Of Pme Under Different Conditionsmentioning

confidence: 99%

Paramagnetic Meissner Effect in Electrochemically Doped Indium-Tin Oxide Films

Aliev

Andrade

Salamon

2016

J Supercond Nov Magn

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“…This fact was confirmed by a number of experiments performed on both conventional [28] and high temperature superconductors [29,30]. The experiments were performed by magneto-optic technique [29] or by using scanning Hall-probes [28,30] on thin conventional superconducting discs [28], HTS films [29] or thin single crystals [30], in the external magnetic field perpendicular to their surfaces. Until now, many attempts have been undertaken to solve the problem of the magnetic field and screening current distribution in superconductors with non-zero demagnetizing factors [31].…”

Section: Discussionmentioning

confidence: 59%

Magnetic flux jumps in texturedBi2Sr2CaCu2

et al. 2003

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Magnetic flux jumps in textured Bi2Sr2CaCu2O 8+δ have been studied by means of magnetization measurements in the temperature range between 1.95 K and Tc, in an external magnetic field up to 9 T. Flux jumps were found in the temperature range 1.95 K -6 K, with the external magnetic field parallel to the c axis of the investigated sample. The effect of sample history on magnetic flux jumping was studied and it was found to be well accounted for by the available theoretical models. The magnetic field sweep rate strongly influences the flux jumping and this effect was interpreted in terms of the influence of both flux creep and the thermal environment of the sample. Strong flux creep was found in the temperature and magnetic field range where flux jumps occur suggesting a relationship between the two. The heat exchange conditions between the sample and the experimental environment also influence the flux jumping behavior. Both these effects stabilize the sample against flux instabilities, and this stabilizing effect increases with decreasing magnetic field sweep rate. Demagnetizing effects are also shown to have a significant influence on flux jumping.

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“…Calculations of the magnetic response of finite superconductors in the critical state including demagnetizing effects have been recently presented for strips [6] and cylinders [7][8][9], following previous works on very thin strips [10] and disks [11]. Very recently, Shantsev et al [12] have discussed important features of the effects of demagnetizing fields in the hysteresis loop.…”

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confidence: 99%

Critical-current density from magnetization loops of finite high-T_csuperconductors

Sanchez

Navau

2001

Supercond. Sci. Technol.

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We analyze the effects of demagnetizing fields in the magnetization hysteresis loops of type-II superconductors, by a model that allows the calculation of current and field profiles in finite cylindrically symmetric superconductors in the critical state. We show how the maximum in the magnetization curve gradually shifts from negative applied field values to the central position with decreasing sample thickness. From the analysis of the calculated field profiles, we demonstrate that one can obtain the intrinsic field-dependent critical-current density of the superconductor with great accuracy by measuring the magnetic response of superconductors with large aspect ratio with the applied field parallel to the shortest dimension.The critical current density J c is one of the key parameters of high-T c superconductors. In particular, knowing the dependence of J c on the internal magnetic field H i = B/µ 0 in the superconductor is a key concern for the study of the current-carrying states of the superconductors. The J c (|H i |) dependence is obtained from two general types of experiments: electrical and magnetic. In electrical transport measurements, the reliability and repeatability of the measured values of the critical current is reduced because of the difficulties in making contacts in the sample and in choosing a voltage criteria for defining J c . Moreover, in general large currents circulate through the sample during the measurements, so that they produce a magnetic field that modifies the applied field in a inhomogeneous way. This makes the estimation of the intrinsic J c (|H i |) dependence difficult. The other general method for obtaining J c is from magnetization measurements, typically isothermal magnetization loops M (H a ), where H a is the applied field. J c is obtained from the width ∆M of the M (H a ) hysteresis loop usingwhere d is a length characteristic of the sample size and geometry; for a cylinder of radius R,This relation follows from the critical-state model [1]. The magnetic method also involves some approximations. First, the method was originally derived for the case of J c independent of [12] have discussed important features of the effects of demagnetizing fields in the hysteresis loop. In particular, they demonstrated theoretically and experimentally that for very thin strips in perpendicular field the peak that appears in the reverse magnetization curve is located not at negative fields, but at the central position.In this work, we systematically study the effect of demagnetizing fields in the magnetic response of finite superconducting cylinders in the presence of a uniform applied field, and discuss the implications in J c extraction. We first introduce a model which allows us to compute current and field profiles and magnetization loops of superconducting cylinders with the same intrinsic parameters but different aspect ratios, in order to study in detail the effects of demagnetizing fields. These will be analyzed in relation to two particular features: the position of the peak in...

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Critical-state model for the determination of critical currents in disk-shaped superconductors

Cited by 174 publications

References 12 publications

Paramagnetic Meissner Effect in Electrochemically Doped Indium-Tin Oxide Films

Paramagnetic Meissner Effect in Electrochemically Doped Indium-Tin Oxide Films

Magnetic flux jumps in texturedBi2Sr2CaCu2

Critical-current density from magnetization loops of finite high-T_csuperconductors

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Critical-state model for the determination of critical currents in disk-shaped superconductors

Cited by 174 publications

References 12 publications

Paramagnetic Meissner Effect in Electrochemically Doped Indium-Tin Oxide Films

Paramagnetic Meissner Effect in Electrochemically Doped Indium-Tin Oxide Films

Magnetic flux jumps in texturedBi2Sr2CaCu2

Critical-current density from magnetization loops of finite high-Tcsuperconductors

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Product

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Critical-current density from magnetization loops of finite high-T_csuperconductors