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

J. Albrecht·A. T. Matveev·J. Strempfer·H. -U. Habermeier·D. V. Shantsev·Y. M. Galperin·T. H. Johansen
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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.

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J. Albrecht, A. T. Matveev, J. Strempfer, H. -U. Habermeier, D. V. Shantsev, Y. M. Galperin, T. H. Johansen. 2006-07-03. Dramatic role of critical current anisotropy on flux avalanches in MgB2 films. https://doi.org/10.1103/physrevlett.98.117001

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