CeFePO: A Heavy Fermion Metal with Ferromagnetic Correlations

TL;DR

CeFePO is a heavy Fermion metal with strong electronic correlations and ferromagnetic correlations, showing no magnetic order but close to a ferromagnetic instability, dominated by Ce-4f electrons.

Contribution

This study provides detailed experimental evidence that CeFePO is a non-magnetic heavy Fermion metal with ferromagnetic correlations, emphasizing the role of Ce-4f electrons over Fe-3d electrons.

Findings

Heavy Fermion behavior with gamma=700mJ/molK2

Presence of ferromagnetic correlations indicated by Wilson ratio and Korringa product

Ce-4f electrons dominate magnetism, not Fe-3d electrons

Abstract

The ground state properties of CeFePO, a homologue of the new high temperature superconductors RFePnO(1-x)Fx, were studied by means of susceptibility, specific heat, resistivity, and NMR measurements on polycrystals. All the results demonstrate that this compound is a magnetically non-ordered heavy Fermion metal with a Kondo temperature TK~10K, a Sommerfeld coefficient gamma=700mJ/molK2 and a mass enhancement factor of the order of 200. The absence of a Fe-contribution to the effective moment at high temperatures indicates that the magnetism in CeFePO is completely dominated by the effect of Ce. Thus the strong electronic correlation effects originate from the Ce-4f electrons rather than from the Fe-3d electrons. An enhanced Sommerfeld-Wilson ratio R=5.5 as well as a Korringa product S0/T1TK2~0.065 well below 1 indicate the presence of ferromagnetic correlations. Therefore, CeFePO appears to be on the non-magnetic side of a ferromagnetic instability.