Normal state resistivity, upper critical field, and Hall effect in superconducting perovskite MgCNi 3

The normal state resistivtity, upper critical field ${H}_{c2}$ and Hall coefficient ${R}_{H}$ in superconducting perovskite ${\mathrm{MgCNi}}_{3}$ ${(T}_{c}\ensuremath{\approx}8 \mathrm{K})$ have been studied. Above 70 K, $\ensuremath{\rho}(T)$ fits well curve predicted by Bloch-Gr\"uneisen theory consistently with electron-phonon scattering. ${H}_{c2}(0)$ was estimated to be about 15.0 T within the weak-coupling BCS theory, and the superconducting coherence length $\ensuremath{\xi}(0)$ is approximately $47 \AA{}.$ ${R}_{H}$ of ${\mathrm{MgCNi}}_{3}$ is negative for the whole temperature range which definitely indicates that the carrier in ${\mathrm{MgCNi}}_{3}$ is electron type. ${R}_{H}$ is temperature independent between ${T}_{c}$ and $\ensuremath{\sim}140 \mathrm{K}.$ Above $\ensuremath{\sim}140 \mathrm{K},$ the magnitude of ${R}_{H}$ decreases as temperature rises. At T=100 K, the carrier density is $1.0\ifmmode\times\else\texttimes\fi{}{10}^{22}/{\mathrm{cm}}^{3},$ which is comparable with that in perovskite $(\mathrm{Ba},\mathrm{K}){\mathrm{BiO}}_{3},$ and less than that of the metallic binary ${\mathrm{MgB}}_{2}.$