Fig.1. Magneto-optical images at T=5 K for an applied magnetic field of 10 mT of MgB2 samples grown by PLD and RD, respectively.

We study the flux penetration in superconductors in static case (only an external magnetic field) and in dynamic case (when in addition to static magnetic field, an Ac current is also applied). In case of MgB2 thin films grown by in situ pulsed laser deposition and in situ reactive technique, we observed a difference in flux penetration. In PLD samples the flux avalanches formed dendritic patterns while in RD samples the flux penetrates more homogeneously and forms finger like structures.

Fig.2. Magnetic flux penetration in nano particle doped YBCO thin film. 

References:
1. Andrea Lucarelli, Stephanie Hümmert, Andrea Chaney, and Gunter Lüpke. Applied Physics Letters. 91(2007), 222505 .

Funding: DoE