The electronic properties of the carbon substituted MgB2 single crystals are reported. The carbon substitution drops Tc below 2 K. In-plane resistivity shows a remarkable increase in residual resistivity by C-substitution, while the change of in-plane/out-of-plane Hall coefficients is rather small. Raman scattering spectra indicate that the E2g-phonon frequency radically hardens with increasing the carbon-content, suggesting the weakening of electron-phonon coupling. Another striking C-effect is the increases of the second critical fields in both in-plane and out-of-plane directions, accompanied by a reduction in the anisotropy ratio. The possible changes in the electronic state and the origin of Tc-suppression by C-substitution are discussed.
@article{arxiv.cond-mat/0312458,
title = {Carbon-substitution effect on the electronic properties of MgB$_2$ single crystals},
author = {T. Masui and S. Lee and S. Tajima},
journal= {arXiv preprint arXiv:cond-mat/0312458},
year = {2009}
}