SiC and carbon nanotube distinctive effects on the superconducting properties of bulk MgB2

• DOI: 10.1063/1.2832463
• Publication Date: 2008-01-22T23:39:06Z
• Authors: G. Serrano; A. Serquis; S. X. Dou; S. Soltanian; L. Civale; B. Maiorov; T. G. Holesinger; F. Balakirev; M. Jaime
• Keywords: Engineering; 0103 physical sciences; 621; 01 natural sciences

This work describes in detail the simultaneous enhancement of the upper critical field (Hc2) and the critical current density (Jc) of MgB2 bulk samples doped with nano-SiC particles, as well as single-walled and double-walled (dw) carbon nanotubes (CNTs). The magnetization properties were examined in a superconducting quantum interference device magnetometer, and four-probe transport measurements were performed using a 50T pulsed magnet to determine Hc2(T). We found that the Jc enhancement is similar in all doped samples at 5K but nano-SiC addition is more effective to improve the flux pinning in the high temperature range (T⩾20K); this improvement cannot solely be attributed to the C incorporation to the lattice but also to the presence of other types of defects (i.e., several kinds of nanoinclusions). CNTs produce a better C incorporation that is more effective to enhance Hc2 [i.e., dwCNT-doped samples reached a record Hc2(0)∼44T value for bulk MgB2]. All the Hc2(T) curves obtained for different types of doping can be successfully described using a model for a two-gap superconductor in the dirty limit.