Magnetic ground state ofCeNi1−xCux: A calorimetric investigation

Abstract

$\mathrm{Ce}{\mathrm{Ni}}_{1-x}{\mathrm{Cu}}_x$ is a substitutional magnetic system where the interplay of the different magnetic interactions leads to the disappearance of the long-range magnetic order on the CeNi side. The existence of inhomogeneities (spin clusters or phase coexistence) has been previously detected by magnetization and muon spin relaxation $\left(\mu \mathrm{SR}\right)$ spectroscopy measurements. These inhomogeneities are always observed regardless of the different preparation methods and must, then, be considered as intrinsic. We present a detailed specific heat study in a large temperature range of $0.2\text{to}300\mathrm{K}$. The analysis of these data, considering also previous neutron scattering, magnetic characterization, and $\mu \mathrm{SR}$ results, allows us to present a convenient description of the system as inhomogeneous on the nanometric scale. Two regimes are detected in the compositional range depending on the dominant Ruderman-Kittel-Kasuya-Yosida or Kondo interactions. We propose that the long-range magnetic order at low temperatures is achieved by a percolative process of magnetic clusters that become static below the freezing temperature $T_f$. In this scenario the existence of a quantum critical point at the magnetic-nonmagnetic crossover must be discarded. This situation should be considered as an example for other substitutional compounds with anomalous magnetic or superconducting properties.