2003/03/03 by S. Jemima Balaselvi, Balaselvi, S. Jemima, A. Bharathi +9
Physics and Astronomy · #Physics of Superconductivity and Magnetism #Superconductivity in MgB2 and Alloys #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/0303022
Submitted to Phys. Rev B on 24th Feb 2003
arxiv created 2003/03/03 · arxiv updated 2009/11/30
The superconducting transition temperature, TC, the residual resistivity ρ0 and the slope of resistivity curve at high temperature, dρ/dT, have been measured in a series of MgB2 samples that have been chemically substituted to varying degree with Li or Cu at the Mg-site and by Li or Cu at the Mg-site along with C substitution at the B-site. DC resistivity and ac susceptibility measurements were employed to extract the above parameters. TC versus the electron count (estimated from simple chemical valence count arguments) shows a universal behaviour, with TC being constant at the MgB2 value for electron counts lower than in MgB2 but rapidly decreasing for larger electron counts. The temperature dependence of resistivity in the normal state fits to the Bloch- Gruneisen formula, from which the Debye temperature, θD, and the ρ0 are extracted. θD variation with TC is not systematic, whereas ρ0 versus TC shows a systematic variation that depends on the type of the chemical substituent. This dependence has a signature of the nature of the intraband/interband scattering affected by the chemical substitutions. dρ/dT increases with C substitution, but decreases with Li and Cu substitution, implying that C substitution leads to the domination of conductivity by the σ band, while in the Li/Cu substituted samples the π band dominates conduction.