Dramatic role of critical current anisotropy on flux avalanches in MgB2 films

Abstract

Anisotropic penetration of magnetic flux in MgB2 films grown on vicinal sapphire substrates is investigated using magneto-optical imaging. Regular penetration above 10 K proceeds more easily along the substrate surface steps, anisotropy of the critical current being 6%. At lower temperatures the penetration occurs via abrupt dendritic avalanches that preferentially propagate {\em perpendicular} to the surface steps. This inverse anisotropy in the penetration pattern becomes dramatic very close to 10 K where all flux avalanches propagate in the strongest-pinning direction. The observed behavior is fully explained using a thermomagnetic model of the dendritic instability.

4 pages, 5 figures

References in corpus (3)

• Dendritic flux avalanches and nonlocal electrodynamics in thin superconducting films
• Onset of dendritic flux avalanches in superconducting films
• Avalanche-driven fractal flux distributions in NbN superconducting films

Cited by in corpus (6)

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• Nanoscale assembly of superconducting vortices with scanning tunnelling microscope tip
• Evidence of rf-driven branching of dendritic vortex avalanches in MgB2 microwave resonators
• Self-recording and manipulation of fast long-range hydrogen diffusion in quasifree magnesium
• Impact of border defects on the magnetic flux penetration in superconducting films
• Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films