Kondo-Cluster-Glass State near a Ferromagnetic Quantum Phase Transition

We report on a comprehensive study of CePd_1-xRhₓ (0.6≤x≤0.95) poly- and single crystals close to the ferromagnetic instability by means of low-temperature ac susceptibility, magnetization, and volume thermal expansion. The signature of ferromagnetism in this heavy-fermion system can be traced from 6.6 K in CePd down to 25 mK for $x=0.87$. Despite pronounced non-Fermi-liquid effects in both specific heat and thermal expansion, the Gr\"uneisen ratio does not diverge as T→0, providing evidence for the absence of a quantum critical point. Instead, a peculiar ``Kondo-cluster-glass'' state is found for x≥0.65, and the non-Fermi-liquid effects in the specific heat, ac susceptibility, and magnetization are compatible with the quantum Griffiths phase scenario.