Portal de Periódicos da CAPES

Magneto-optical studies of the critical states in c-axis oriented MgB/sub 2/ thin film and bulk MgB/sub 2/=Mg nano-composites

2003; IEEE Council on Superconductivity; Volume: 13; Issue: 2 Linguagem: Inglês

10.1109/tasc.2003.812526

1558-2515

Zuxin Ye, Qiang Li, Genda Gu, Jiajing Tu, W. N. Kang, Eun-Mi Choi, Hyeong-Jin Kim, Sung-Ik Lee,

Iron-based superconductors research

We present magneto optical (MO) studies of the critical states in a c-axis oriented MgB/sub 2/ thin film with a critical current density (J/sub c/) of 6 MA/cm/sup 2/ at 5 K, and bulk MgB/sub 2//Mg nano-composites with J/sub c/ over 1 MA/cm/sup 2/ at 5 K. The magnetic flux penetration and trapping in the thin film are found remarkably different from that in the bulk samples. A tree-like magnetic flux pattern was observed entering the superconducting film, as well as various complex dendritic flux jumps due to the thermo-magnetic instability. These behaviors indicate the collapse of the critical state of a type II superconductor at local level. In contrast, a regular flux penetration into the critical state was observed in the bulk nano-composites, which indicates that the addition of pure Mg helps to stabilize the critical state.