Heavy-fermion-like excitations in metallic ${\mathrm{Nd}}_{2\mathrm{-}\mathit{y}}$${\mathrm{Ce}}_{\mathit{y}}$${\mathrm{CuO}}_4$

The specific heat of ${\mathrm{Nd}}_{2\mathrm{-}\mathit{y}}$ ${\mathrm{Ce}}_{\mathit{y}}$ ${\mathrm{CuO}}_4$, 0≤y≤0.2, was measured between 35 mK and 10 K. A Schottky anomaly in ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$, due to exchange interactions between Nd and Cu moments, shifts upon Ce doping to lower temperatures. In the metallic state (y≥0.15), a linear term with coefficient γ≃4J/${\mathrm{K}}^2$ per mole Nd is found below 300 mK. For y=0.2, a constant value of the magnetic susceptibility in the same temperature range and changes of ${\mathit{C}}_{\mathit{p}}$ in applied magnetic fields suggest an interpretation in analogy to a heavy-fermion system resulting from the coupling between Nd moments and conduction electrons.