Strongly linked current flow in polycrystalline forms of the new superconductor MgB2

摘要: The discovery of superconductivity at 39 K in MgB2[1] raises many issues. One the central questions is whether this new superconductor resembles a high-temperature-cuprate or low-temperature metallic terms its current carrying characteristics applied magnetic fields. In spite very high transition temperatures cuprate superconductors, their performance fields has several drawbacks[2]. Their large anisotropy restricts bulk densities to much less than full field-temperature (H-T) space over which found. Further, weak coupling across grain boundaries makes transport untextured polycrystalline forms low and strongly field sensitive[3,4]. These studies MgB2 address both multi-phase, untextured, nano-scale sub-divided nature our samples, supercurrents flow throughout without strong sensitivity characteristic Josephson-coupled grains[3]. Magnetization measurements nearly all superconducting H-T plane show good temperature scaling flux pinning force, suggestive density determined by pinning. At least two length scales are suggested magnetization magneto optical (MO) analysis but cause seems be phase inhomogeneity, porosity, minority insulating such as MgO rather weakly coupled boundaries. Our results suggest that ceramics class will not compromised link problems conclusion with enormous significance for applications if higher analogs compound can discovered.