Confinement and quantization effects in mesoscopic superconducting structures

Moshchalkov, Victor; Bruyndoncx, V.; Rosseel, Erik; Look, Lieve Van; Baert, M.; Bael, M. J. Van; Puig, Teresa; Strunk, Christoph; Bruynseraede, Y.

doi:10.1063/1.55274

Cited by 3 publications

(2 citation statements)

References 36 publications

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“…Recent progress in nanofabrication has stimulated both experimental and theoretical studies of nanostructured materials and individual nanostructures [1].…”

Section: Introductionmentioning

confidence: 99%

Conductivity and magnetoresistance of crystals with superconducting nanoscale inclusions

Sugakov

Shevtsova

2000

Supercond. Sci. Technol.

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The temperature dependence of conductivity and conductivity as a function of the magnetic field for a non-conducting crystal with superconducting inclusions have been calculated. In the calculations the assumption was made that the inclusion radius is less than or of the order of the coherence length and the inclusion concentration is insufficient for onset of superconductivity in a whole sample (i.e. below the percolation threshold). It was shown that the presence of superconducting inclusions leads to a sharp increase in conductivity of a sample at low temperatures, and to a strong dependence of conductivity on the magnetic field (magnetoresistance). Influence of dispersion of inclusion sizes on the conductivity as a function of temperature and magnetic field has been studied.

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“…Recent progress in nanofabrication has stimulated both experimental and theoretical studies of nanostructured materials and individual nanostructures [1].…”

Section: Introductionmentioning

confidence: 99%

Conductivity and magnetoresistance of crystals with superconducting nanoscale inclusions

Sugakov

Shevtsova

2000

Supercond. Sci. Technol.

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“…1 Arguably among the most relevant of these goals is the increase of the critical field below which superconductivity nucleates. For a given material this effect can be achieved by doping the starting compound in such a way that the electronic mean free path ᐉ becomes smaller than the superconducting coherence length ͑Ref.…”

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confidence: 99%

Optimization of superconducting critical parameters by tuning the size and magnetization of arrays of magnetic dots

et al. 2007

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We investigate the nucleation of superconductivity in an Al film deposited on top of an array of micromagnets with perpendicular anisotropy by dc transport measurements. The absolute control of the magnetic state of the ferromagnets enabled us to explore the superconductor-normal-metal phase boundary as a function of the magnetization M of the dots. For a given external homogeneous field H, the magnetization of the dots can be tuned in such a way to optimize the field and current compensation in the sample, thus yielding a clear enhancement of the upper critical field H c2 . In addition, we theoretically demonstrate that the critical current I c for a given temperature could be further enhanced by properly adjusting the size of the magnetic dots. These results are fully corroborated by the Ginzburg-Landau theory as well as analytic estimates. DOI: 10.1103/PhysRevB.76.100502 PACS number͑s͒: 74.78.Fk, 74.25.Dw, 74.25.Fy Controlling the critical parameters of superconductors has been a long pursued objective of condensed matter physicists.1 Arguably among the most relevant of these goals is the increase of the critical field below which superconductivity nucleates. For a given material this effect can be achieved by doping the starting compound in such a way that the electronic mean free path ᐉ becomes smaller than the superconducting coherence length ͑Ref. 2͒ or by nanopatterning the material in order to promote surface superconductivity.3 Both cases manifest themselves as an enhancement of the upper critical field by a field-independent factor which is determined by either ᐉ or the geometrical details of the nanostructuring.An alternative way of preventing the deterioration of the superconducting state under external magnetic fields consists of locally counteracting the applied field by introducing an array of micrometer-sized paramagnets with high magnetic susceptibility. 4 In this case superconductivity would nucleate in the interstitial position between neighboring paramagnets where the returning stray field of the magnetic elements nearly compensates the external field, 5 and thus higher fields than in normal conditions could be sustained. 6 A very close approximation to this situation can be achieved by using a periodic array of ferromagnets with a tunable magnetic moment m aligned with the applied field H. In this case, unlike for the paramagnets, by changing the polarity of the magnetic moments of the dots one can counteract the external homogeneous field either above ͑m and H antiparallel͒ or in between the magnetic elements ͑m and H parallel͒.7 These field-compensation effects can lead to a substantial increase of the upper critical field in a field-temperature region determined by the magnetization of the dots.In this work, we study the field compensation effects in an Al thin film evaporated on top of a square array of Co/ Pt microdots with tunable out-of-plane magnetization. The selected materials give rise to a sizable difference between the magnetic and superconducting characteristic energies wh...

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Tunable pinning in superconducting films with magnetic microloops

Silhanek

Gillijns

Moshchalkov

et al. 2006

Applied Physics Letters

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We study the flux pinning properties of superconductor/magnetic micro-rings lattice hybrid structures. The used open triangular micromagnets represent an eight-fold degree of freedom system, with six polarized and two flux-closure possible states. By conveniently choosing the magnetic state of the underlying rings it is possible to induce different pinning potentials. We show that the magnetic vortex state with minimum stray field produces a weaker pinning in comparison with the polarized states.

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Confinement and quantization effects in mesoscopic superconducting structures

Cited by 3 publications

References 36 publications

Conductivity and magnetoresistance of crystals with superconducting nanoscale inclusions

Conductivity and magnetoresistance of crystals with superconducting nanoscale inclusions

Optimization of superconducting critical parameters by tuning the size and magnetization of arrays of magnetic dots

Tunable pinning in superconducting films with magnetic microloops

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