Ferromagnetic Quantum Critical Point in Heavy-Fermion Iron Oxypnictide Ce(Ru${}_{1-x}$Fe${}_x$)PO

Abstract

We have performed ^{31}P-NMR measurements on Ce(Ru_{1-x}Fe_{x})PO in order to investigate ferromagnetic (FM) quantum criticality, since heavy-fermion (HF) ferromagnet CeRuPO with a two-dimensional structure turns to a HF paramagnet by an isovalent Fe-substitution for Ru. We found that Ce(Ru_{0.15}Fe_{0.85})PO shows critical fluctuations down to \sim 0.3 K, as well as the continuous suppression of Curie temperature and the ordered moments by the Fe-substitution. These experimental results suggest the presence of a FM quantum critical point (QCP) at x \sim 0.86, which is a rare example among itinerant ferromagnets. In addition, we point out that the critical behaviors in Ce(Ru_{0.15}Fe_{0.85})PO share the similarity with those in YbRh_{2}Si_{2}, where the local criticality of $f$ electrons has been discussed. We reveal that Ce(Ru_{1-x}Fe_{x})PO is a new system to study FM quantum criticality in HF compounds.

5 pages, 5 figures, accepted for publication in Physical Review Letters

References in corpus (4)

• Heavy Fermions and Quantum Phase Transitions
• Formation of a Nematic Fluid at High Fields in Sr3Ru2O7
• CeRuPO: A rare example of a Ferromagnetic Kondo lattice
• CeFePO: A Heavy Fermion Metal with Ferromagnetic Correlations

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• Avoided ferromagnetic quantum critical point in CeRuPO
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• Phase diagram of CeRuPO under pressure investigated by ${}^{31}$P-NMR - Comparison between CeRuPO under pressure and the Ce(Ru${}_{1-x}$Fe${}_x$)PO system -
• Magnetocrystalline anisotropic effect in GdCo${}_{1-x}$Fe${}_x$AsO ($x=0,0.05$)