Measurements of magnetic screening lengths in superconducting Nb thin films by polarized neutron reflectometry

Zhang, Huai; Lynn, J. W.; Majkrzak, C. F.; Satija, Sushil K.; Kang, Joonhee; Wu, X. D.

doi:10.1103/physrevb.52.10395

Cited by 43 publications

(49 citation statements)

References 25 publications

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“…For the Nb single layers we find a small Meissner expulsion with a field penetration depth of 270 nm (I) and 160 nm (II) respectively. These value are much larger than the typical 30 nm found for clean Nb systems [9][10][11] but are not inconsistent with results on dirty systems (similar to those considered here) where the penetration length increases with decreasing mean free path and values up to 230 nm have been observed [12,13]. For the Cu/Nb bilayers we find an enhancement of the Meissner expulsion, which we verify by theory.…”

supporting

confidence: 68%

Observation of Anomalous Meissner Screening in Cu/Nb and Cu/Nb/Co Thin Films

et al. 2018

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We have observed the spatial distribution of magnetic flux in Nb, Cu/Nb and Cu/Nb/Co thin films using muon-spin rotation. In an isolated 50 nm thick Nb film we find a weak flux expulsion (Meissner effect) which becomes significantly enhanced when adding an adjacent 40 nm layer of Cu. The added Cu layer exhibits a Meissner effect (due to induced superconducting pairs) and is at least as effective as the Nb to expel flux. These results are confirmed by theoretical calculations using the quasiclassical Green's function formalism. An unexpected further significant enhancement of the flux expulsion is observed when adding a thin (2.4 nm) ferromagnetic Co layer to the bottom side of the Nb. This observed cooperation between superconductivity and ferromagnetism, by an unknown mechanism, forms a key ingredient for developing superconducting spintronics.

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supporting

confidence: 68%

Observation of Anomalous Meissner Screening in Cu/Nb and Cu/Nb/Co Thin Films

et al. 2018

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“…This yields L ϭ490 Ϯ110 Å, in agreement with previous work. 5,6 In order to observe the effect of vortices, the reflectivity was measured as a function of applied field at a single position of 2ϭ0.38°, where ⌬R/R exhibits the first maximum. Figure 3 shows the results for ascending and descending fields.…”

Section: Resultsmentioning

confidence: 99%

“…Further refinement of this technique for Nb by Zhang et al 6 included the effect of the electron mean free path on L . The same technique was also used to determine L for high-temperature superconducting oxides.…”

Section: Introductionmentioning

confidence: 99%

Orientation of vortices in a superconducting thin film: Quantitative comparison of spin-polarized neutron reflectivity and magnetization

et al. 2000

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We present a quantitative comparison of the magnetization measured by spin-polarized neutron reflectivity ͑SPNR͒ and dc magnetometry on a 1370 Å-thick Nb superconducting film. As a function of magnetic field applied in the film plane, SPNR exhibits reversible behavior whereas the dc magnetization shows substantial hysteresis. The difference between these measurements is attributed to a rotation of the vortex magnetic field out of the film plane as the applied field is reduced. SPNR measures only the magnetization parallel to the film plane, whereas dc magnetization is strongly influenced by the perpendicular component of magnetization when there is a slight sample tilt; thus combining the two techniques allows one to distinguish two components of magnetization in a thin film.

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“…11 The technique has also been applied to measure the London penetration depth L in conventional 12,13 as well as HTC superconductors.…”

Section: Introductionmentioning

confidence: 99%

Spin-polarized neutron reflectivity: A probe of vortices in thin-film superconductors

et al. 1999

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It is demonstrated that the specular reflectivity of spin-polarized neutrons can be used to study vortices in a thin-film superconductor. Experiments were performed on a 6000 Å thick c-axis film of YBa 2 Cu 3 O 7Ϫx with the magnetic field applied parallel to the surface. A magnetic hysteresis loop was observed for the spinpolarized reflection and, from these data, the average density of vortices was extracted. A model is presented which relates the specular reflectivity to the one-dimensional spatial distribution of vortices in the direction perpendicular to the surface. Unlike other techniques, neutron reflectivity observes vortices in a geometry where they are parallel to the interface. ͓S0163-1829͑99͒07021-6͔

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Measurements of magnetic screening lengths in superconducting Nb thin films by polarized neutron reflectometry

Cited by 43 publications

References 25 publications

Observation of Anomalous Meissner Screening in Cu/Nb and Cu/Nb/Co Thin Films

Observation of Anomalous Meissner Screening in Cu/Nb and Cu/Nb/Co Thin Films

Orientation of vortices in a superconducting thin film: Quantitative comparison of spin-polarized neutron reflectivity and magnetization

Spin-polarized neutron reflectivity: A probe of vortices in thin-film superconductors

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