Nano-SiC and carbon nanotubes distinctive effects on the superconducting properties of bulk MgB2

G. SERRANO; A SERQUIS; S. X. DOU; S. SOLTANIAN; L. CIVALE; B. MAIOROV; T. G. HOLESINGER; F. BALAKIREV; M. JAIME

JOURNAL OF APPLIED PHYSICS

American Institute of Physics

Año: 2008 vol. 103 p. 23907 - 23907

0021-8979

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 50 T pulsed magnet to determine Hc2(T).We found that the Jc enhancement is similar in all doped samples at 5 K but nano-SiC addition is more effective to improve the flux pinning in the high temperature range (T>20 K); 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)= 44 T 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.