Rigid vortices in MgB2
Hao Jin, Hai-Hu Wen, Hai-Peng Yang, Zhi-Yong Liu, Zhi-An Ren, Guang-Can Che, Zhong-Xian Zhao
Abstract
Magnetic relaxation of high-pressure synthesized MgB
2
bulks with different thickness is investigated. It is found that the superconducting dia-magnetic moment depends on time in a logarithmic way; the flux-creep activation energy decreases linearly with the current density (as expected by Kim-Anderson model); and the activation energy increases linearly with the thickness of sample when it is thinner than about 1 mm. These features suggest that the vortices in the MgB
2
are rather rigid, and the pinning and creep can be well described by Kim-Anderson model.