Multiband superconductivity in Co-doped SrFe 2As 2 investigated using local magnetic imaging

Waled M Desoky, Simon J Bending, S E Sebastian

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Abstract

High resolution scanning Hall probe microscopy and Hall magnetometry have been used to investigate the magnetic properties of superconducting Co-doped SrFe 2xCo xAs 2 single crystals. We resolve rather disordered field-cooled vortex structures at all values of the applied field studied, present due to the strong vortex pinning arising from substitution of Fe with Co. We have fitted the profiles of well-isolated vortices as a function of temperature in order to extract mesoscopic estimates of the temperature dependence of the magnetic field penetration depth,λ . These data were then used to calculate the superfluid density (ρ s) over the full temperature range and fitted to a two-band -model with two full gaps. The results suggest that the superfluid density is shared almost equally between hole and electron pockets and that the larger (electron pocket) gap appears to have an approximately isotropic s-wave order parameter. Displacements of the vortices from an ideal triangular lattice have been used to estimate the low field pinning forces which are several orders of magnitude smaller than values estimated by other means for similar superconducting crystals.
Original languageEnglish
Article number045011
JournalSuperconductor Science and Technology
Volume25
Issue number4
DOIs
Publication statusPublished - 2012

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Superconductivity
Vortex flow
superconductivity
vortices
Imaging techniques
Electrons
estimates
Temperature
magnetic measurement
Magnetic properties
Microscopic examination
electrons
Substitution reactions
penetration
Single crystals
substitutes
Magnetic fields
magnetic properties
microscopy
Scanning

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Multiband superconductivity in Co-doped SrFe 2As 2 investigated using local magnetic imaging. / Desoky, Waled M; Bending, Simon J; Sebastian, S E.

In: Superconductor Science and Technology, Vol. 25, No. 4, 045011, 2012.

Research output: Contribution to journalArticle

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AB - High resolution scanning Hall probe microscopy and Hall magnetometry have been used to investigate the magnetic properties of superconducting Co-doped SrFe 2xCo xAs 2 single crystals. We resolve rather disordered field-cooled vortex structures at all values of the applied field studied, present due to the strong vortex pinning arising from substitution of Fe with Co. We have fitted the profiles of well-isolated vortices as a function of temperature in order to extract mesoscopic estimates of the temperature dependence of the magnetic field penetration depth,λ . These data were then used to calculate the superfluid density (ρ s) over the full temperature range and fitted to a two-band -model with two full gaps. The results suggest that the superfluid density is shared almost equally between hole and electron pockets and that the larger (electron pocket) gap appears to have an approximately isotropic s-wave order parameter. Displacements of the vortices from an ideal triangular lattice have been used to estimate the low field pinning forces which are several orders of magnitude smaller than values estimated by other means for similar superconducting crystals.

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