Normal state resistivity, upper critical field and Hall effect in superconducting perovskite $MgCN{i}_3$

Abstract

The normal state resistivtity, upper critical field $H_{c2}$ and Hall coefficient $R_H$ in superconducting perovskite $MgCN{i}_3$ ($T_c\approx 8K$) have been studied. Above 70 K, $\ddot{I}(T)$ fits well curve predicted by Bloch-Grüneisen theory consistently with electron-phonon scattering. $H_{c2}(0)$ was estimated to be about 15.0 Tesla within the weak-coupling BCS theory, and the superconducting coherence length $\hat{I}¾(0)$ is approximately 47 à . $R_H$ of $MgCN{i}_3$ is negative for the whole temperature range which definitely indicates that the carrier in $MgCN{i}_3$ is electron-type. $R_H$ is temperature independent between $T_c$ and $\sim$ 140 K. Above $\sim$ 140 K, the magnitude of $R_H$ decreases as temperature rises. At T = 100 K, the carrier density is $1.0\times 10^{22}/c{m}^3$, which is comparable with that in perovskite $(Ba,K)Bi{O}_3$, and less than that of the metallic binary $Mg{B}_2$.

sample quality improved, new figures, submitted to Phys. Rev. B