Carbon-substitution effect on the electronic properties of MgB 2 single crystals
2004; American Physical Society; Volume: 70; Issue: 2 Linguagem: Inglês
10.1103/physrevb.70.024504
ISSN1550-235X
Autores Tópico(s)Thermal Expansion and Ionic Conductivity
ResumoThe electronic properties of the carbon substituted MgB$_2$ single crystals are reported. The carbon substitution drops T$_c$ 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 E$_{2g}$-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 T$_c$-suppression by C-substitution are discussed.
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