Pinning in superconducting films with triangular lattice of holes

Lykov, A. N.

doi:10.1016/0038-1098(93)90103-t

Cited by 58 publications

(33 citation statements)

References 2 publications

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“…Another feature of the series we ascribe to the phenomenon of 'matching fields' [84]. In experiments concerned with the arrangements of vortices in periodic arrangements of defects, it is found that the vortex lattice is most ordered when the field is such that the periodicity of the vortices is a simple multiple of the periodicity of the defects.…”

Section: Correlation Analysis Of Fluxon Lattice As a Function Of Magnmentioning

confidence: 98%

Imaging flux vortices in type II superconductors with a commercial transmission electron microscope

Loudon¹,

Midgley²

2009

Ultramicroscopy

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Flux vortices in superconductors can be imaged using transmission electron microscopy because the electron beam is deflected by the magnetic flux associated with the vortices. This technique has a better spatial and temporal resolution than many other imaging techniques and is sensitive to the magnetic flux density within each vortex, not simply the fields at the sample surface. Despite these advantages, only two groups have successfully employed the technique using specially adapted instruments. Here we demonstrate that vortices can be imaged with a modern, commercial transmission electron microscope operating at 300 kV equipped with a field emission gun, Lorentz lens and a liquid helium cooled sample holder. We introduce superconductivity for non-specialists and discuss techniques for simulating and optimising images of flux vortices. Sample preparation is discussed in detail as the main difficulty with the technique is the requirement for samples with very large (>10µm), flat areas so that the image is not dominated by diffraction contrast. We have imaged vortices in superconducting Bi 2 Sr 2 CaCu 2 O 8-δ and use correlation functions to investigate the ordered arrangements they adopt as a function of applied magnetic field.

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Section: Correlation Analysis Of Fluxon Lattice As a Function Of Magnmentioning

confidence: 98%

Imaging flux vortices in type II superconductors with a commercial transmission electron microscope

Loudon¹,

Midgley²

2009

Ultramicroscopy

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“…Because shielding currents flow circularly over the film and traverse normally to cross section of the film as illustrated in Fig. 5, magnetization caused from the immanent defects after the introduction of the artificial pinning centers, , is given as (5) where is the size of the sample and is film thickness. We can estimate by inserting groove period, , and width, , into (5).…”

Section: A Magnetization Of the Nb Filmmentioning

confidence: 99%

“…As main parameters in such a periodic pinning centers, there are size, period, and depth of them. Previous researches have demonstrated flux pinning effect of lattice-like hole patterns fabricated with an electron beam direct writing [5], [6] and periodic groove patterns with a laser expo- sure etc. [7], [8] as artificial pinning centers.…”

Section: Introductionmentioning

confidence: 99%

Periodic artificial pinning centers for high critical current density of tape conductor

Yamada

Harada

Iwamoto

et al. 2002

IEEE Trans. Appl. Supercond.

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In order to achieve high magnetic field in superconducting magnet, superconducting tape conductor with effective pinning centers is required for high critical current density. We studied periodic artificial pinning centers for the scope of use in HTS tape conductor. Periodic patterns were introduced as artificial pinning centers on a superconducting Nb film. To investigate the effect of flux pinning, 2 and 4 m period groove patterns were formed on the Nb film with various depths. Magnetization and critical current density of the films with the groove patterns were larger than those of the film without the pattern, as a result of effective artificial pinning. After regarding immanent magnetization caused by defects, films with 2 m period grooves had about 2 times as much increase of magnetization as the films with 4 m period grooves. Ratio of pinning force density of 2 m period groove pattern to that of 4 m period groove pattern was calculated to be 2, and we found this calculated value is in good agreement with the experimental one. The magnetization of both films increased with groove depth until that reached a half of film thickness. It is considered that this increase of magnetization with groove depth is mainly caused by an increase of elementary pinning force for individual flux line.

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“…[1][2][3] Recently attention has focused on investigations of flux pinning in regular ͑periodic͒ arrays of artificial pinning sites. [4][5][6][7][8] This interest arises from the fact that arrays of pinning centers can stabilize ordered vortex configurations leading to striking anomalies in the magnetization [6][7][8] and the critical current. 5,9 The existence of these anomalies is attributed to commensurability effects and has been extensively studied both experimentally 6-10 and theoretically.…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6][7][8] This interest arises from the fact that arrays of pinning centers can stabilize ordered vortex configurations leading to striking anomalies in the magnetization [6][7][8] and the critical current. 5,9 The existence of these anomalies is attributed to commensurability effects and has been extensively studied both experimentally 6-10 and theoretically. [10][11][12] Since most natural type-II superconducting materials contain randomly distributed pinning sites it is worthwhile investigating vortex interactions with controlled irregular ͑ran-dom͒ arrays of pinning centers ͑e.g., columnar defects͒ to gain better insight into their properties.…”

Section: Introductionmentioning

confidence: 99%

Flux-line interactions with precipitates inYBa2Cu3O7<

et al. 2000

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We have used scanning Hall probe microscopy to study the interaction between flux lines and a random array of precipitates in thin YBCO films. Pinning by precipitates has been demonstrated by measuring the distribution and magnetic field profiles of individual flux lines. Flux lines in the film with precipitates have strongly preferred locations as well as a much broader range of shapes and sizes compared to YBCO films without precipitates. We have also observed ''local magnetization'' anomalies, which appear at multiples of the matching field for the random array of pinning sites.

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Pinning in superconducting films with triangular lattice of holes

Cited by 58 publications

References 2 publications

Imaging flux vortices in type II superconductors with a commercial transmission electron microscope

Imaging flux vortices in type II superconductors with a commercial transmission electron microscope

Periodic artificial pinning centers for high critical current density of tape conductor

Flux-line interactions with precipitates inYBa2Cu3O7<

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