Simulation of Field Dependence of Critical Current Densities of Bulk High T_c Superconducting Materials regarding Thermally Activated Flux Motion

In the upcoming generation, bulk high temperature superconductors (HTS) will play a crucial and a promising role in numerous industrial applications ranging from Maglev trains to magnetic resonance imaging, etc. Especially, the bulk HTS as permanent magnets are suitable due to the fact that they can trap magnetic fields being several orders of magnitude higher than those of the best hard ferromagnets. The bulk HTS LREBa₂Cu₃O_7-δ (LREBCO or LRE-123, LRE: Y, Gd, etc.,) materials could obtain very powerful compact superconducting super-magnets, which can be operated at the cheaper liquid nitrogen temperature or below due to higher critical temperatures (i.e., ∼90 K). As a result, the new advanced technology can be utilized in a more attractive manner for a variety of technological and medical applications which have the capacity to revolutionize the field. An understanding of the magnetic field dependence of the critical current density (J_c(H)) is important to develop better adapted materials. To achieve this goal, a variety of J_c (H) behaviours of bulk LREBCO samples were modelled regarding thermally activated flux motion. In essence, the J_c (H) curves follows a certain criterion where an exponential model is applied. However, to fit the complete J_c (H) curve of the LRE-123 samples an unique model is necessary to explain the behavior at low and high fields. The modelling of the various superconducting materials could be understood in terms of the pinning mechanisms.