Planar current anisotropy and field dependence of <i>J</i> <sub>c</sub> in coated conductors assessed by scanning Hall probe microscopy

Lao, Mayraluna; Hecher, J; Sieger, Max; Pahlke, Patrick; Bauer, Markus; Hühne, Ruben; Eisterer, M.

doi:10.1088/1361-6668/30/2/024004

Cited by 18 publications

(16 citation statements)

References 33 publications

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“…Measurements of solid-angle dependence, J c (B, θ, φ) with φ being the angle of B with the current density, are scarce for any type of sample [56] and missing for this particular tape. The cause is the complexity of the measurements, requiring a double goniometer [58][59][60][61]. The model uses J c (B, θ) data for both components J x and J y , and hence there is discrepancy between the model and the real measurements in the highest cross-fields.…”

Section: F Comparison Of Cross-field Demagnetization In a Stack Of Ta...mentioning

confidence: 99%

Cross-field demagnetization of stacks of tapes: 3D modelling and measurements

Kapolka¹,

Pardo

Grilli³

et al. 2019

Supercond. Sci. Technol.

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Stacks of superconducting tapes can trap much higher magnetic fields than conventional magnets. This makes them very promising for motors and generators.However, ripple magnetic fields in these machines present a cross-field component that demagnetizes the stacks. At present, there is no quantitative agreement between measurements and modeling of cross-field demagnetization, mainly due to the need of a 3D model that takes the end effects and real micron-thick superconducting layer into account. This article presents 3D modeling and measurements of cross-field demagnetization in stacks of up to 5 tapes and initial magnetization modeling of stacks of up to 15 tapes. 3D modeling of the cross-field demagnetization explicitly shows that the critical current density, J c , in the direction perpendicular to the tape surface does not play a role in cross-field demagnetization. When taking the measured anisotropic magnetic field dependence of J c into account, 3D calculations agree with measurements with less than 4 % deviation, while the error of 2D modeling is much higher. Then, our 3D numerical methods can realistically predict cross-field demaga This article has been published in Supercond. Sci. Technol. with netization. Due to the force-free configuration of part of the current density, J, in the stack, better agreement with experiments will probably require measuring the J c anisotropy for the whole solid angle range, including J parallel to the magnetic field.the probe is at least 10 mV/T. Cross-field demagnetization consists on the following three main steps: magnetization by field cooling (FC) method, relaxation time and cross-field demagnetization. The detailed process is the following:• The sample is placed into the electromagnet at room temperature.• The electromagnet is ramped up to 1 T.• The sample is cooled down in liquid nitrogen bath at 77 K.• The electromagnet is ramped down with ramp rate 10 mT/s. 400 405 410 415 420 425 B t /B 0 [-] t [s] cal 50 mT cal 100 mT cal 150 mT cal 50 mT n(B,θ) cal 100 mT n(B,θ) cal 150 mT n(B,θ) (b) FIG. 19: (a) The n(B, θ) measured data on a 4 mm wide SuperOx tape, measured in Bratislava by the set-up in [46]. (b) The comparison of calculation with constant n=30 and n(B, θ) dependence, both cases use J c (B, θ) dependence. Using n(B, θ) slightly reduces the demagnetization rate for a few number of cycles, but later on it is increased slightly.

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Section: F Comparison Of Cross-field Demagnetization In a Stack Of Ta...mentioning

confidence: 99%

Cross-field demagnetization of stacks of tapes: 3D modelling and measurements

Kapolka¹,

Pardo

Grilli³

et al. 2019

Supercond. Sci. Technol.

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“…The magnetic response of the tape was analysed using Bean's critical state model [2] with a spatially independent , which leads to the well established 'rooftop' internal field distribution that has been confirmed experimentally using Hall probe microscopy [3]. For ACS measurements, analytic expressions for Ac susceptibility, ′′, were used [4].…”

Section: Introductionmentioning

confidence: 99%

Comparison of ${J_{{C}}}$ in GdBCO Tape Using Dc Magnetization and Harmonic Ac Susceptibility Measurements

Smith

Surrey

Moon

et al. 2018

IEEE Trans. Appl. Supercond.

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“…In cuprates, for instance, the critical current density in the c crystallographic axis is much smaller than in the ab plane. There is also important anisotropy in REBCO vicinal films due to flux channeling [23,24].The "de-pinning" anisotropy of J c is due to anisotropic maximum pinning forces caused by either anisotropic pinning centres or anisotropic vortex cores [25]. When the current density J is perpendicular to B and the electric field E is parallel to J, the anisotropy of J c is always due to de-pinning anisotropy.…”

mentioning

confidence: 99%

3D modelling of macroscopic force-free effects in superconducting thin films and rectangular prisms

Kapolka¹,

Pardo²

2019

Supercond. Sci. Technol.

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When the magnetic field has a parallel component to the current density J there appear force-free effects due to flux cutting and crossing. This results in an anisotropic E(J) relation, being E the electric field. Understanding force-free effects is interesting not only for the design of superconducting power and magnet applications but also for material characterization.This work develops and applies a fast and accurate computer modeling method based on a variational approach that can handle force-free anisotropic E(J) relations and perform fully three dimensional (3D) calculations. We present a systematic study of force-free effects in rectangular thin films and prisms with several finite thicknesses under applied magnetic fields with arbitrary angle θ with the surface. The results are compared with the same situation with isotropic E(J) relation.The thin film situation shows gradual critical current density penetration and a general increase of the magnitude of the magnetization with the angle θ but a minimum at the remnant state of the magnetization loop. The prism model presents current paths with 3D bending for all angles θ. The average current density over the thickness agrees very well with the thin film model except for the highest angles.The prism hysteresis loops reveal a peak after the remnant state, which is due to the parallel component of the self-magnetic-field and is implicitly neglected for thin films.The presented numerical method shows the capability to take force-free situations into account for general 3D situations with a high number of degrees of freedom.The results reveal new features of force-free effects in thin films and prisms.Type II superconductors are essential for large bore or high-field magnets [1][2][3][4] and are promising for power applications, such as motors for air-plane [5,6] or ship propulsion [7,8], generators [9][10][11], grid power-transmission cables [12,13], transformers [14][15][16][17], and or fault-current limiters [18][19][20][21][22]. The Critical Current Density, J c , of type II superconductors depends on the magnitude and angle of the local magnetic field. There are three types of anisotropy which we call "intrinsic", "de-pinning", and "force free" anisotropy.The "intrinsic" anisotopy is the following. Certain superconductors present an axis with suppressed superconductivity, where the critical current density is lower. In cuprates, for instance, the critical current density in the c crystallographic axis is much smaller than in the ab plane. There is also important anisotropy in REBCO vicinal films due to flux channeling [23,24].The "de-pinning" anisotropy of J c is due to anisotropic maximum pinning forces caused by either anisotropic pinning centres or anisotropic vortex cores [25]. When the current density J is perpendicular to B and the electric field E is parallel to J, the anisotropy of J c is always due to de-pinning anisotropy. This kind of anisotropy is important for High-Temperature Superconductors (HTS), such as (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10 and ...

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Planar current anisotropy and field dependence of J _c in coated conductors assessed by scanning Hall probe microscopy

Cited by 18 publications

References 33 publications

Cross-field demagnetization of stacks of tapes: 3D modelling and measurements

Cross-field demagnetization of stacks of tapes: 3D modelling and measurements

Comparison of ${J_{{C}}}$ in GdBCO Tape Using Dc Magnetization and Harmonic Ac Susceptibility Measurements

3D modelling of macroscopic force-free effects in superconducting thin films and rectangular prisms

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Planar current anisotropy and field dependence of J c in coated conductors assessed by scanning Hall probe microscopy

Cited by 18 publications

References 33 publications

Cross-field demagnetization of stacks of tapes: 3D modelling and measurements

Cross-field demagnetization of stacks of tapes: 3D modelling and measurements

Comparison of ${J_{{C}}}$ in GdBCO Tape Using Dc Magnetization and Harmonic Ac Susceptibility Measurements

3D modelling of macroscopic force-free effects in superconducting thin films and rectangular prisms

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Planar current anisotropy and field dependence of J _c in coated conductors assessed by scanning Hall probe microscopy