Magnetic properties of cobalt-covered MgB2 films

A heterostructure of MgB2 and cobalt was investigated using SQUID magnetometry and magneto-optical (MO) imaging. Two different effects are observed. On the one hand, the temperature for the occurrence of flux avalanches is shifted to lower temperatures T-a as observed by MO studies. On the other hand, magnetic hysteresis loops (MHLs) obtained by SQUID measurements show a significant asymmetry with respect to the H-ext = 0 axis attributed to magnetic effects on flux line pinning. Interestingly, the position of the central peak of the MHLs is shifted to positive fields H-cp.