Peculiar quantum criticality in ferromagnetic ${\mathrm{CePd}}_{1-x}{\mathrm{Rh}}_x$

Abstract

The alloy ${\mathrm{CePd}}_{1-x}{\mathrm{Rh}}_x$ is a unique example undergoing quantum critical behavior between ferromagnetic CePd $(T_{\mathrm{C}}=6.6\mathrm{K})$ and mixed valence CeRh. The negative curvature of $T_{\mathrm{C}}(x)$ holds up to $x=0.6$, followed by a positive tail with the lowest measured $T_{\mathrm{C}}=0.25\mathrm{K}$ at $x=0.80$. We report on a detailed investigation within the $0.80⩽x⩽1$ range, using specific heat $(C_m)$ and thermal expansion $(\beta )$ techniques. A change of regime is observed in the T dependence of both parameters at $x_{\mathrm{cr}}=0.85$, from $\ln (T_0/T)$ to $A(x)T^{-q}$, with $q=0.54$ at $x=0.87$ and the coefficient $A(x)$ vanishing as $x\to 1$. Simultaneously, a change of sign in $\beta (T)$ is observed at $x_{\mathrm{cr}}$. The vanishing $C_m/T$=$A(x)T^{-q}$ contribution coexists beyond $x_{\mathrm{cr}}$ with a Fermi Liquid component.