Magnetization relaxation and collective vortex pinning in the Fe-based superconductor SmFeAsO_(0.9)F_(0.1)

摘要

By measuring the dynamic and traditional magnetization relaxations we investigate the vortex dynamics of the recently discovered superconductor SmFeAsO_(0.9)F_(0.1) with T_c=55 K. It is found that the relaxation rate is rather large reflecting a small characteristic pinning energy. Moreover it shows a weak temperature dependence in wide temperature region, which resembles the behavior of the cuprate superconductors. Combined with the resistivity data under different magnetic fields, a vortex phase diagram is obtained. Our results strongly suggest that the model of collective vortex pinning applies to this superconductor very well.