Electron scattering dependence of dendritic magnetic instability in superconducting MgB2 films

Magnetic instability in both ultrapure and carbon-doped MgB2 films is investigated by magneto-optical imaging, transport, and bulk magnetization measurements. In the carbon-doped MgB2 thin films, familiar dendritic flux-jump patterns were observed at low temperature as reported in previous experiments. In the ultrapure MgB2 thin film, however, a remarkably stable flux penetration was observed, clearly showing the classic behavior of the critical state model. Such different behavior indicates that the electron scattering ultimately controls the magnetic stability of the MgB2 films.