Pressure effects on the transition temperature of superconducting ${\mathrm{MgC}}_x{\mathrm{Ni}}_3$

The effect of hydrostatic pressure $\mathrm{}\left(P\right)\mathrm{}$ up to 17 kbar on the superconducting transition temperature ${(T}_{\mathrm{C}})$ of the newly discovered intermetallic nonoxide perovskite superconductor ${\mathrm{MgC}}_x{\mathrm{Ni}}_3$ has been reported. $T_{\mathrm{C}}$ is found to increase with increasing $P$ at a rate of ${\mathrm{dT}}_{\mathrm{C}}/dP\sim 0.0134$ to 0.0155 K/kbar depending on the value of carbon content $x.\mathrm{}$ The absolute value of ${\mathrm{dT}}_{\mathrm{C}}/dP$ for ${\mathrm{MgC}}_x{\mathrm{Ni}}_3$ is about the same as that of intermetallic $R{\mathrm{Ni}}_2{\mathrm{B}}_2\mathrm{C}$ $(R$ denotes rare earth) and metallic superconductors but about one order of magnitude smaller than that of the most recently and intensively studied superconductor ${\mathrm{MgB}}_2.$ However, the $d\ln T_{\mathrm{C}}/dP\sim 0.00181$ to $0.00224{\mathrm{kbar}}^{-1}$ and the rate of change of $T_{\mathrm{C}}$ with unit cell volume (V), $d\ln T_{\mathrm{C}}/d\ln V\sim -3.18$ to $-2.58$ of ${\mathrm{MgC}}_x{\mathrm{Ni}}_3$ are having the comparable magnitude to that of ${\mathrm{MgB}}_2$ with opposite sign. The increase of $T_{\mathrm{C}}$ with $P$ in ${\mathrm{MgC}}_x{\mathrm{Ni}}_3$ can be explained in the framework of density of states (DOS) effect.