Indication of Ferromagnetic Quantum Critical Point in Kondo Lattice CeRh₆Ge₄

Abstract

We report resistivity measurements under pressure for Kondo-lattice ferromagnet CeRh 6 Ge 4 , 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 CeRh 6 Ge 4 , to the contrary, the Curie temperature of 2.5 K 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 CeRh 6 Ge 4 shows the FM QCP at zero field. Band structure calculation suggests the unusual electronic state of CeRh 6 Ge 4 among Ce-based Kondo lattices. CeRh 6 Ge 4 deserves further investigations and will be a key material to understand the matter of the FM QCP.

Anisotropic c−f Hybridization in the Ferromagnetic Quantum Critical Metal CeRh6Ge4Wu1, Zhang2, Du3 et al. 2021Phys. Rev. Lett.333160View full textAdd to dashboardCite

“…Here, we present ARPES results on CeRh 6 Ge 4 , a FM HF compound with Curie temperature T C ¼ 2.5 K at ambient pressure. T C can be continuously suppressed to zero by pressure, resulting in a FM QCP at p c ¼ 0.8 GPa [1,13]. It was theoretically proposed that the FM QCP in the zero temperature limit involves a simultaneous breakdown of the Kondo screening, resulting in an abrupt jump in Fermi surface (FS) volume from a "large FS" incorporating 4f electrons in the high-pressure paramagnetic phase to a "small FS" that does not contain 4f electrons in the lowpressure FM phase [1,14].…”

Magnetic order and crystalline electric field excitations of the quantum critical heavy-fermion ferromagnet CeRh6Ge4

“…* msmidman@zju.edu.cn Recently, the heavy fermion ferromagnet CeRh 6 Ge 4 with a Curie temperature T C = 2.5 K [16] was found to be an exception to this paradigm, from the findings that hydrostatic pressure continuously suppresses T C , yielding a FM QCP [17,18]. The QCP is accompanied by a strange metal phase, with a linear temperature dependence of the resisitivity and a logarithmic divergence of the specific-heat coefficient [17].…”

Magnetic and Transport Properties of a New Kondo-Lattice Compound Ce3NbRh4Ge4

“…In fact, the existence of RE 3 NbRh 4 Ge 4 has been reported only for RE = Ce, Pr, and Nd [4]. The magnetization M(T, H) was measured using a superconducting quantum interference device magnetometer (Quantum Design, MPMS) as functions of the temperature T and magnetic field H between 1.8 and 300 K up to 5 T. The electrical resistivity (T) was measured with a dc four-probe method between 0.4 and 294 K in a laboratory-built 3 He cryostat. The ac magnetic susceptibility  ac (T) was measured with a field-modulation method with frequency 100 Hz and modulation field 0.1 mT between 0.4 and 4.2 K in a 3 He cryostat.…”

“…The small magnetic entropy released at 2.5 K (0.19Rln2, where R is the gas constant) and the large electronic specific-heat coefficient (0.25 J/mol K 2 ) indicate that CeRh 6 Ge 4 is a rare FM compound with a vicinity of a QCP [2]. Recent electrical-resistivity measurements under high pressure have corroborated the presence of the FM QCP at zero field or at least in the immediate vicinity of zero field [3]. Subsequently, we have searched for new FM compounds with quantum criticallity and have focused on a new compound Ce 3 NbRh 4 Ge 4 .…”