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Local threshold field for dendritic instability in superconducting MgB2 films

F. L. Barkov·D. V. Shantsev·T. H. Johansen·P. E. Goa·W. N. Kang·H. J. Kim·E. M. Choi·S. I. Lee
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Abstract

Using magneto-optical imaging the phenomenon of dendritic flux penetration in superconducting films was studied. Flux dendrites were abruptly formed in a 300 nm thick film of MgB2 by applying a perpendicular magnetic field. Detailed measurements of flux density distributions show that there exists a local threshold field controlling the nucleation and termination of the dendritic growth. At 4 K the local threshold field is close to 12 mT in this sample, where the critical current density is 10^7 A/cm^2. The dendritic instability in thin films is believed to be of thermo-magnetic origin, but the existence of a local threshold field, and its small value are features that distinctly contrast the thermo-magnetic instability (flux jumps) in bulk superconductors.

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F. L. Barkov, D. V. Shantsev, T. H. Johansen, P. E. Goa, W. N. Kang, H. J. Kim, E. M. Choi, S. I. Lee. 2002-05-29. Local threshold field for dendritic instability in superconducting MgB2 films. https://doi.org/10.1103/physrevb.67.064513

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