Dendritic flux patterns in MgB₂films

Abstract

Magneto-opitcal studies of a c-oriented epitaxial MgB2 film with critical\ncurrent density 10^7 A/cm^2 demonstrate a breakdown of the critical state at\ntemperatures below 10 K [cond-mat/0104113]. Instead of conventional uniform and\ngradual flux penetration in an applied magnetic field, we observe an abrupt\ninvasion of complex dendritic structures. When the applied field subsequently\ndecreases, similar dendritic structures of the return flux penetrate the film.\nThe static and dynamic properties of the dendrites are discussed.\n