Normal state resistivity, upper critical field, and Hall effect in superconducting perovskiteMgCNi3

The normal state resistivtity, upper critical field $H_{c2\mathrm{}}$ and Hall coefficient $R_H$ in superconducting perovskite ${\mathrm{MgCNi}}_3$ ${(T}_c\approx 8\hspace{0.5em}\mathrm{K})$ have been studied. Above 70 K, $\rho \mathrm{}\left(T\right)\mathrm{}$ fits well curve predicted by Bloch-Grüneisen theory consistently with electron-phonon scattering. $H_{c2\mathrm{}}\mathrm{}\left(0\right)\mathrm{}$ was estimated to be about 15.0 T within the weak-coupling BCS theory, and the superconducting coherence length $\xi \mathrm{}\left(0\right)\mathrm{}$ is approximately $47\hspace{0.5em}\AA .$ $R_H$ 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 $\sim 140\hspace{0.5em}\mathrm{K}.$ Above $\sim 140\hspace{0.5em}\mathrm{K},$ the magnitude of $R_H$ decreases as temperature rises. At T=100 K, the carrier density is $1.0\times {10}^{22}/{\mathrm{cm}}^3,$ which is comparable with that in perovskite $(\mathrm{Ba},\mathrm{K}){\mathrm{BiO}}_3,$ and less than that of the metallic binary ${\mathrm{MgB}}_2.$