Transition from magnetic to nonmagnetic ground state in a heavy-fermion compound Ce7Ni3 under high pressure

The electrical resistivity and ac magnetic susceptibility of the heavy-fermion compound Ce7Ni3 were measured in the temperature range from 0.4 to 300 K and in the pressure range up to 1.5 GPa. The Neel 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, rho(m)=rho(Ce7Ni3)-rho(La7Ni3), decreases steeply with pressure, and above 0.66 GPa, rho(m)(T) can be described by the expression rho(m)(T)=rho(m)(0)+AT(2). The coefficient A decreases and the temperature range in which the T-2 dependence is held becomes wider with increasing pressure. The electronic Gruneisen parameter for the Kondo temperature T-K, -partial derivative lnT(K)/partial derivative 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 Ce7Ni3.