Indication of ferromagnetic quantum critical point in Kondo lattice CeRh₆Ge₄

We report resistivity measurements under pressure for Kondo-lattice ferromagnet CeRh₆Ge₄, and present that a quantum ferromagnetic (FM) phase transition is easily achieved. In most clean metallic ferromagnets, a quantum critical point (QCP) at zero field is avoided by changing the FM transition to a discontinuous transition or to an antiferromagnetic transition. In CeRh₆Ge₄, to the contrary, the Curie temperature of 2.5K decreases continuously as increasing pressure without any clear signature that the transition changes to first order. The obvious non Fermi liquid behavior is observed in the vicinity of the quantum FM phase transition. The experimental data do not contradict a picture in which CeRh₆Ge₄ shows the FM QCP at zero field. Band structure calculation suggests the unusual electronic state of CeRh₆Ge₄ among Ce-based Kondo lattices. CeRh₆Ge₄ deserves further investigations and will be a key material to understand the matter of the FM QCP. (author)