Magnetic order and crystalline electric field excitations of the quantum critical heavy fermion ferromagnet CeRh${}_6$Ge${}_4$

Abstract

CeRh${}_6$Ge${}_4$ is an unusual example of a stoichiometric heavy fermion ferromagnet, which can be cleanly tuned by hydrostatic pressure to a quantum critical point. In order to understand the origin of this anomalous behavior, we have characterized the magnetic ordering and crystalline electric field (CEF) scheme of this system. While magnetic Bragg peaks are not resolved in neutron powder diffraction, coherent oscillations are observed in zero-field $\mu$SR below $T_{\mathrm{C}}$, which are consistent with in-plane ferromagnetic ordering consisting of reduced Ce moments. From analyzing the magnetic susceptibility and inelastic neutron scattering, we propose a CEF-level scheme which accounts for the easy-plane magnetocrystalline anisotropy, where the low lying first excited CEF exhibits significantly stronger hybridization than the ground state. These results suggest that the orbital anisotropy of the ground state and low lying excited state doublets are important for realizing anisotropic electronic coupling between the $f$- and conduction electrons, which gives rise to the highly anisotropic hybridization observed in photoemission experiments.

7 pages, 4 figures

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Cited by in corpus (12)

• A unified theory of ferromagnetic quantum phase transitions in heavy fermion metals
• Probing quantum criticality in ferromagnetic CeRh6Ge4
• Suppression of ferromagnetism and influence of disorder in silicon-substituted CeRh6Ge4
• Suppression of ferromagnetism governed by a critical lattice parameter in CeTiGe$\_3$ with hydrostatic pressure or V substitution
• Evolution of short-range magnetic correlations in ferromagnetic Ni-V alloys
• From localized 4f electrons to anisotropic exchange interactions in ferromagnetic CeRh6Ge4
• Importance of anisotropic interactions for hard-axis/plane ordering of Ce-based ferromagnets
• Observation of field-induced single-ion magnetic anisotropy in a multiorbital Kondo alloy $(\mathrm{Lu},\mathrm{Yb}){\mathrm{Rh}}_2{\mathrm{Zn}}_{20}$
• Magnetic properties of $R$Rh${}_6$Ge${}_4$ ($R$ = Pr, Nd, Sm, Gd-Er) single crystals
• Distinct effect of Kondo physics on crystal field splitting in electron and spin spectroscopies
• The Kondo effect in ferromagnetic quantum critical CeRh${}_6$Ge${}_4$
• Non-collinear ferromagnetism in the Kondo lattice Ce${}_5$CoGe${}_2$