Transition from magnetic to nonmagnetic ground state in a heavy-fermion compoundCe7Ni3

The electrical resistivity and ac magnetic susceptibility of the heavy-fermion compound ${\mathrm{Ce}}_{7}$${\mathrm{Ni}}_{3}$ were measured in the temperature range from 0.4 to 300 K and in the pressure range up to 1.5 GPa. The N\'eel temperature of 1.9 K for antiferromagnetic transition at ambient pressure decreases with increasing pressure and vanishes at about 0.33 GPa. The magnetic resistivity, ${\mathrm{\ensuremath{\rho}}}_{\mathit{m}}$=\ensuremath{\rho}(${\mathrm{Ce}}_{7}$${\mathrm{Ni}}_{3}$)-\ensuremath{\rho}(${\mathrm{La}}_{7}$${\mathrm{Ni}}_{3}$), decreases steeply with pressure, and above 0.66 GPa, ${\mathrm{\ensuremath{\rho}}}_{\mathit{m}}$(T) can be described by the expression ${\mathrm{\ensuremath{\rho}}}_{\mathit{m}}$(T)=${\mathrm{\ensuremath{\rho}}}_{\mathit{m}}$(0)+${\mathit{AT}}^{2}$. The coefficient A decreases and the temperature range in which the ${\mathit{T}}^{2}$ dependence is held becomes wider with increasing pressure. The electronic Gr\"uneisen parameter for the Kondo temperature ${\mathit{T}}_{\mathit{K}}$, -\ensuremath{\partial}ln${\mathit{T}}_{\mathit{K}}$/\ensuremath{\partial}lnV, is evaluated to be 132 from the pressure dependence of A. This value is larger than that of typical heavy-fermion compounds. The results are discussed in relation to the competition between the magnetic interaction and the Kondo interaction in ${\mathrm{Ce}}_{7}$${\mathrm{Ni}}_{3}$. \textcopyright{} 1996 The American Physical Society.