Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd1−xLaxNiC2 compounds

The path from the charge density wave antiferromagnet NdNiC2 to the noncentrosymmetric superconductor LaNiC2 is studied by gradual replacement of Nd by La ions. The evolution of physical properties is explored by structural, magnetic, transport, magnetoresistance, and specific heat measurements. With the substitution of La for Nd, the Peierls temperature is gradually suppressed, which falls within the BCS mean-field relation for chemical pressure with a critical concentration of xc=0.38. As long as the charge density wave (CDW) is maintained, the antiferromagnetic (AFM) ground state remains robust against doping and, despite a Néel temperature reduction, shows a rapid and sharp magnetic transition. Once the CDW is completely suppressed, intermediate compounds of the Nd1−xLaxNiC2 series reveal symptoms of a gradual softening of the features associated with the AFM transition and an increase of the spin disorder. Immediately after the antiferromagnetic transition is depressed to zero temperature, the further incorporation of La ions results in the emergence of superconductivity. This crossover in Nd1−xLaxNiC2 is discussed in terms of the possible quantum critical point.