Analysis of Critical State Response in Thin Films by AC Susceptibility Measurements

Youssef, Ahmed; Švindrych, Zdeněk; Hadač, J.; Janú, Z.

doi:10.1109/tasc.2008.922391

Cited by 8 publications

(9 citation statements)

References 9 publications

(12 reference statements)

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“…Low-T c superconductors were investigated a long time ago [1][2][3] and revealed an absorption maximum at the transition upon variation of temperature and dc magnetic field. The ac response of high-T c superconductors exhibits similar features [4][5][6]. However, the physical reasons for this behavior remain unclear.…”

Section: Introductionmentioning

confidence: 99%

“…The ac magnetic response contains essential information about the properties of superconductors. Peculiarities of the ac response of conventional and high-T c superconductors have been a matter of extensive research [1][2][3][4][5][6]. Low-T c superconductors were investigated a long time ago [1][2][3] and revealed an absorption maximum at the transition upon variation of temperature and dc magnetic field.…”

Section: Introductionmentioning

confidence: 99%

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dc and ac magnetic properties of thin-walled superconducting niobium cylinders

et al. 2014

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We report the results of an experimental study of the dc and ac magnetic properties of superconducting Nb thin-walled cylinders in parallel to the axis magnetic fields. The magnetization curves at various temperatures are measured. Surprisingly, at 4.5 K, for magnetic fields much lower than H c1 , avalanchelike jumps of the magnetization are observed. The position of the jumps is not reproducible and changes from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures larger than 6.5 K, the measured magnetization curves become smooth. ac response is measured in constant and swept dc magnetic fields. A phenomenological model that describes the ac response of the surface superconducting states is proposed. This model assumes that the observed ac response in dc fields larger than H c2 is due to the relaxation of surface superconducting states with nonzero current in the walls to the state with zero current, and the existence of a critical current below which this relaxation is absent.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

dc and ac magnetic properties of thin-walled superconducting niobium cylinders

et al. 2014

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“…The first was an 8-pixel array consisting of STJs with a size of 50 × 50 µm 2 , which was used to measure the full currentvoltage (I-V ) curves. Because the critical current (I C ) of the superconducting Nb wirings (cross-section ∼ 1.2 × 10 −7 cm 2 ) used in the STJs was less than 0.1 Å, [7] it was necessary to use STJs with a size of 50 ×50 µm 2 to prevent the current flow in the Nb wirings from exceeding the I C values of the Nb wirings when J C was measured. The second was a 100-pixel array of STJs with a size of 100 × 100 µm 2 , which was used to evaluate the x-ray detection performance.…”

Section: Methodsmentioning

confidence: 99%

Characteristics of Nb/Al superconducting tunnel junctions fabricated using ozone gas

Ukibe¹,

Fujii²,

Ohkubo³

2015

Chinese Phys. B

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To improve the energy resolution (ΔE) of Nb/Al superconducting tunnel junctions (STJs), an ozone (O3) oxidation process has been developed to fabricate a thin defect-free tunnel barrier that simultaneously shows high critical current JC > 1000 A/cm2 and high normalized dynamic resistance RDA > 100 MΩ · μm2, where A is the size of the STJ. The 50-μm2 STJs produced by O3 exposure of 0.26 Pa· min with an indirect spray of O3 gas, which is a much lower level of exposure than the O2 exposure used in a conventional O2 oxidation process, exhibit a maximum JC = 800 A/cm2 and a high RDA = 372 MΩ · μm2. The 100-pixel array of the 100-μm2 STJs produced using the same O3 oxidation conditions exhibits a constant leak current Ileak = 14.9 ± 3.2 nA at a bias point around Δ /e (where e is half the energy gap of an STJ), and a high fabrication yield of 87%. Although the Ileak values are slightly larger than those of STJs produced using the conventional O2 oxidation process, the STJ produced using O3 oxidation shows a ΔE = 10 eV for the C-Kα line, which is the best value of our Nb/Al STJ x-ray detectors.

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“…In this paper we reanalyze earlier measurements on Nb film [6] using a method first applied to the YBCO wire and we compare the results.…”

Section: Introductionmentioning

confidence: 99%

“…We have shown that this model correctly predicts the response of the YBCO wire and allows estimate in a contactless way the critical current density and its temper-ature dependence [5]. In this paper we reanalyze earlier measurements on Nb film [6] using a method first applied to the YBCO wire and we compare the results.…”

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confidence: 99%

Contactless Estimation of Critical Current Density and Its Temperature Dependence Using Magnetic Measurements

et al. 2010

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We have measured magnetic response of second-generation high temperature superconductor YBa 2 Cu 3 O x wire and Nb thin film in perpendicular ac field as a function of temperature. We compare experimental complex ac susceptibility to the calculated susceptibility based on the model of Bean's critical-state response in two-dimensional disk in perpendicular field. The harmonic analysis is needed for comparison between the model and the experimental data. We present a method of linking model and experimental susceptibility. Good agreement of experimental susceptibility with model susceptibility of 2D disk allows contactless estimation of critical depinning current density and its temperature dependence.

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Analysis of Critical State Response in Thin Films by AC Susceptibility Measurements

Cited by 8 publications

References 9 publications

dc and ac magnetic properties of thin-walled superconducting niobium cylinders

dc and ac magnetic properties of thin-walled superconducting niobium cylinders

Characteristics of Nb/Al superconducting tunnel junctions fabricated using ozone gas

Contactless Estimation of Critical Current Density and Its Temperature Dependence Using Magnetic Measurements

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