Vortex Pinning and Flux Flow Microwave Studies of Coated Conductors

Pompeo, Nicola; Torokhtii, Kostiantyn; Alimenti, Andrea; Mancini, A.; Celentano, G.; Silva, Enrico

doi:10.1109/tasc.2019.2897956

Cited by 4 publications

(3 citation statements)

References 33 publications

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“…t layer stands here for the thickness of specified layers. Following transmission line analogy and impedance transformation 23 , the effective measured surface impedance of the CCs Z CC can be written as with being the surface impedance of the superconductor (valid in the local limit) and ρ the complex resistivity 24,25 . Z stack is the effective measured surface impedance of the layers below the superconductor (dielectric buffer layers/metallic substrate) and k SC = µ 0 2πν…”

Section: Resultsmentioning

confidence: 99%

High frequency response of thick REBCO coated conductors in the framework of the FCC study

Романов

Krkotić

Telles

et al. 2020

Sci Rep

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z www.nature.com/scientificreports/ commercially available CCs have shown lower R s than 300 µm thick Cu colaminated on stainless steel (equivalent of FCC beam screen) at T = 50 K and ν = 8 GHz up to 9 T. In addition, we demonstrated compatibility with thin a-C layers to mitigate the secondary electron yield 11. In this work, we extend the temperature range of measured surface resistances to T = 20−70 K. It allows a discussion about the surface resistance and vortex physics of CCs with different microstructures in a wide range of temperatures. The vortex parameters depinning frequency ν 0 , vortex viscosity η and Labusch parameter k p are derived within the Gittleman-Rosenblum and Bardeen-Stephen models. The model proposed by Gittleman and Rosenblum 12 is a mean-field theory for vortices in a periodic pinning potential driven by high frequency oscillating, subcritical currents without thermal activation. It modulates both the resistive and reactive response of vortices to the driving field. In our case, the lack of complete surface reactance data sets has to be compensated by additional model confinements. With a modified Bardeen-Stephen model 13 , which describes the motion of vortices in a type II superconductor, we can estimate the vortex viscosity η. It reduces the Gittleman-Rosenblum model parameters to only one, the depinning frequency ν 0 , and thus makes it available through fitting the measured surface resistance R s. We validate the two model approach for one sample with the ratio of surface reactance and surface resistance at T = 20 K , which lets us determine the depinning frequency sticking exclusively to the Gittleman-Rosenblum model. Finally, having established the microwave vortex parameters, we extrapolate the surface impedance of CCs down to 1 GHz , up to 16 T and compare it to the microwave response of Cu at FCC-hh conditions.

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Section: Resultsmentioning

confidence: 99%

High frequency response of thick REBCO coated conductors in the framework of the FCC study

Романов

Krkotić

Telles

et al. 2020

Sci Rep

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“…By increasing T , ∆R, and thus dissipation, increases as expected by approaching T c . Moreover, no steep rise is detected in the low field region, which would be a signature of weak links with the related Josephson or Abrikosov-Josephson vortices [50][51][52], pointing to a good connectivity of the film.…”

Section: Resultsmentioning

confidence: 95%

Pinning properties of FeSeTe thin film through multifrequency measurements of the surface impedance

Pompeo,

Torokhtii,

Alimenti

et al. 2020

Preprint

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We present high frequency measurements of the vortex dynamics of a FeSe x Te 1−x (x = 0.5) thin film grown on a CaF 2 substrate and with a critical temperature T c ≃ 18 K, performed by means of a dual frequency dielectric resonator at 16.4 GHz and 26.6 GHz. We extract and discuss various important vortex parameters related to the pinning properties of the sample, such as the characteristic frequency ν c , the pinning constant k p and the pinning barrier height U relevant for creep phenomena. We find that the vortex system is in the single-vortex regime, and that pinning attains relatively high values in terms of k p , indicating significant pinning at the high frequencies here studied. The pinning barrier energy U is quite small and exhibits a non-monotonous temperature dependence with a maximum near 12 K. This result is discussed in terms of core pinning of small portion of vortices of size ∝ ξ 3 jumping out of the pinning wells over very small distances, a process which is favoured in the high frequency, short ranged vortex oscillations here explored.

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“…On the other hand, surface impedance measurements at microwave (MW) frequencies (at ca. 50 GHz) have been utilized to study the response of YBCO films with different types of nano-inclusions [42][43][44] and CCs [45] in the regime of vortices rapidly shaking within their pinning wells. MW measurements allow to extract information [46] about the depinning frequency ν p , the flux-flow resistivity ρ ff , the pinning constant k p , as well as to disentangle the intrinsic and effective anisotropies of the nanostructured films [47][48][49].…”

Section: Introductionmentioning

confidence: 99%

Vortex pinning properties at dc and microwave frequencies of YBa₂Cu₃O_7-x films with nanorods and nanoparticles

Bartolomé

Alcalà

Vallès

et al. 2020

Supercond. Sci. Technol.

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YBa2Cu3O7−x (YBCO) nanocomposites for wire applications need to operate in a broad range of frequencies, ranging from dc in magnets to GHz in cavities and screenings of future particle accelerators. We have investigated the in-field and angular vortex pinning performance in dc and at 50 GHz of two types of nanocomposites, pulsed laser deposition (PLD) YBCO with mixed Ba2YNbO6 + Ba2YTaO6 (BYNTO) nanorods and chemical solution deposited (CSD) YBCO with BaHfO3 (BHO) nanoparticles (NPs), and the pristine counterpart films, grown on top of single-crystalline substrates. Transport measurements performed up to 9 T between 5-77 K show that CSD nanocomposites exhibit a smooth field decay and increased single-tocollective crossover field H* compared to pristine samples, associated to the enhanced isotropic pinning contribution induced by the NPs, while PLD films exhibit unchanged H* and superior critical current densities up to higher irreversibility fields, associated to the anisotropic contribution introduced by the rods. Microwave in-field measurements of the pinning constant kp revealed CSD NCs exhibit a qualitatively similar, but smoother kp(H) than pristine samples, whereas for PLD samples, a growing kp(H) dependence is observed as a result of the increased relevance of the stiffness of the fluxons pinned by nanorods.

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Vortex Pinning and Flux Flow Microwave Studies of Coated Conductors

Cited by 4 publications

References 33 publications

High frequency response of thick REBCO coated conductors in the framework of the FCC study

High frequency response of thick REBCO coated conductors in the framework of the FCC study

Pinning properties of FeSeTe thin film through multifrequency measurements of the surface impedance

Vortex pinning properties at dc and microwave frequencies of YBa₂Cu₃O_7-x films with nanorods and nanoparticles

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Vortex Pinning and Flux Flow Microwave Studies of Coated Conductors

Cited by 4 publications

References 33 publications

High frequency response of thick REBCO coated conductors in the framework of the FCC study

High frequency response of thick REBCO coated conductors in the framework of the FCC study

Pinning properties of FeSeTe thin film through multifrequency measurements of the surface impedance

Vortex pinning properties at dc and microwave frequencies of YBa2Cu3O7-x films with nanorods and nanoparticles

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Vortex pinning properties at dc and microwave frequencies of YBa₂Cu₃O_7-x films with nanorods and nanoparticles