Energy of dendritic avalanches in thin-film superconductors

Abstract

A method for calculating stored magnetic energy in a thin superconducting film based on quantitative magneto-optical imaging is developed. Energy and magnetic moment are determined with these calculations for full hysteresis loops in a thin film of the superconductor NbN. Huge losses in energy are observed when dendritic avalanches occur. Magnetic energy, magnetic moment, sheet current and magnetic flux distributions, all extracted from the same calibrated magneto-optical images, are analyzed and discussed. Dissipated energy and the loss in moment when dendritic avalanches occur are related to each other. Calculating these losses for specific spatially-resolved flux avalanches is a great advantage, because of their unpredictable and non-reproducible nature. The relative losses in energy are much higher than the relative losses in moment.

Quantitative magneto-optical imaging with ferrite garnets

“…As the magnetization g is derived from B z by a Fourier transformation and Eq. 4.17, it should be of little surprise that it is possible to do magnetometry with Faraday magneto-optical imaging [19]. A practical implementation of this procedure requires properly calibrated magneto-optical images that must again cover a significantly larger area than the sample in order to yield correct results.…”