Inhomogeneous Magnetic Field Penetration in Superconducting Niobium Films

Abal’osheva, I.; Abal’oshev, A.; Cieplak, Marta Z.; Zhu, Leyi; Chien, C. L.

doi:10.12693/aphyspola.118.396

Cited by 5 publications

(4 citation statements)

References 13 publications

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“…Besides that, their morphology is profoundly influenced by the geometry of the defect and its lattice symmetry [53]. Film thickness also influences the flux avalanches since thinner samples require a lower applied magnetic field to trigger the first avalanche [54][55][56]. These abrupt flux penetrations may be detrimental to applications because an avalanche can locally destroy the superconducting state [49].…”

Section: Introductionmentioning

confidence: 99%

Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films

et al. 2022

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Thickness uniformity is regarded as an important parameter in designing thin film devices. However, some applications based on films with nonuniform thickness have recently emerged, such as gas sensors and optimized materials based on the gradual change of film composition. This work deals with superconducting Pb thin films with a thickness gradient prepared with the aid of a diffuse stencil mask. Atomic force microscopy and energydispersive x-ray spectroscopy show variations in the range 90 nm-154 nm. Quantitative magneto-optical images reveal interesting features during both the abrupt and the smooth penetration regimes of magnetic flux, as well as the thickness-dependent critical current density (J c ). In addition, we observe a gradual superconducting transition as the upper critical field is progressively reached for certain thicknesses. Furthermore, the hysteresis observed for triggering flux avalanches when increasing and decreasing magnetic fields is also accounted for by the J c profile evolution along the thickness gradient. Numerical simulations based on the thermomagnetic model are in fair agreement with the experimental data. These findings demonstrate that wedge-shaped films are a viable approach to investigate, in a continuous fashion, thickness-dependent properties of superconducting materials.

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Section: Introductionmentioning

confidence: 99%

Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films

et al. 2022

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“…These crystals are 122 iron arsenides, where barium is partially substituted by potassium. Their critical temperature T c measured by magnetic susceptibility was approximately 35 K. The uniformity of the critical current densities of all crystals was verified using magneto-optic measurements [6] which were carried out at 30 K in perpendicular magnetic fields up to 50 mT. A magneto-optic picture of sample RS 2 is shown in Fig.…”

Section: Samplesmentioning

confidence: 80%

Microwave Characterization of 122-Pnictides by a Superconducting Niobium Cavity

et al. 2019

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We present first results of our microwave measurements of Ba1−xKxFe2As2 (with x = 0.34) single-crystal pnictide, using a cylindrical superconducting niobium microwave cavity, working at approximately 26.2 GHz in the TE011-mode. The measured samples, after initial magneto-optic tests of their uniformity, are cut and glued on a sapphire rod, whose temperature can be independently controlled between 5 K and 40 K. Microwave measurements are performed by a vector network analyzer in the reflection mode, i.e. the S11 component of the complex scattering matrix S is measured. The loaded quality factor QLs and the shift of the resonance position are measured during a temperature sweep, followed by calculating of the unloaded quality factor Q0s and the resonance frequencies fLs and f0s by means of the Kajfez procedure where the subscript "s" denotes the sample. The values of the superconducting penetration depth change δλL and of the surface resistance Rs are calculated approximating the single crystal sample by a flat cylindrical disk of appropriate size, based on a procedure described by Maier and Slater.

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“…where κ is the thermal conductivity of the superconducting film, j c is the temperature derivative of the critical current density, h 0 is the heat transfer coefficient between the film and the substrate, parameter n defines nonlinearity of the current-voltage characteristics in the flux creep regime, E ∝ j n , where E is an electric field. Some aspects of the appearance and behavior of avalanches in niobium films as a function of film thickness have been studied by us [9] and others [10][11][12], but the correlation between such thickness-dependent behavior and the thermal properties of the superconducting material and the film-substrate interface has not yet been studied experimentally. In this paper, we report an investigation of both temperature and film thickness dependence of the H th and l th in Nb films deposited on the glass substrates, and on the basis of the above theoretical model [3,4], we obtain the thermal conductivity, the film-to-substrate heat transfer coefficient or Kapitza thermal boundary conductance (TBC), and the critical current density of our films.…”

Section: Introductionmentioning

confidence: 99%

Thermomagnetic Instabilities in Nb Films Deposited on Glass Substrates

2023

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In this work, we provide a systematic study of the magnetic field penetration process and avalanche formation in niobium films of different thicknesses deposited on glass substrates. The research was carried out by means of direct visualization of the magnetic flux using magneto-optical imaging. The experimental data were compared with theoretical predictions for the development of thermomagnetic instabilities in the form of a finger or dendritic flux avalanches in thin films. Analysis of the temperature and thickness dependence of the threshold magnetic field at which the superconductor first becomes unstable, as well as the flux penetration depth corresponding to this field, allows the evaluation of the thermal and superconducting parameters of the studied films, such as heat transfer coefficient across the film-substrate boundary, thermal conductivity, critical current density.

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Inhomogeneous Magnetic Field Penetration in Superconducting Niobium Films

Cited by 5 publications

References 13 publications

Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films

Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films

Microwave Characterization of 122-Pnictides by a Superconducting Niobium Cavity

Thermomagnetic Instabilities in Nb Films Deposited on Glass Substrates

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