Ferromagnetic Quantum Critical Point Induced by Tuning the Magnetic Dimensionality of the Heavy-Fermion Iron Oxypnictide Ce(Ru$_{1-x}$Fe$_x$)PO

TL;DR

This study uses NMR measurements to explore how tuning magnetic dimensionality via Fe substitution induces a ferromagnetic quantum critical point in Ce(Ru$_{1-x}$Fe$_x$)PO, revealing a unique mechanism distinct from typical heavy-fermion systems.

Contribution

It demonstrates that Fe substitution suppresses out-of-plane magnetic fluctuations, leading to a two-dimensional ferromagnetic quantum critical point in a heavy-fermion compound.

Findings

Out-of-plane fluctuations are suppressed with increasing Fe content.

A two-dimensional ferromagnetic quantum critical point is observed.

The mechanism differs from conventional heavy-fermion quantum criticality.

Abstract

We have performed 31P-NMR measurements of the c-axis-aligned poly-crystal Ce(Ru1-xFex)PO with a two-dimensional layered structure in order to understand the origin of TCurie suppression by Fe substitution. The variation in the magnetic-fluctuation character with respect to x is investigated from the in-plane and out-of plane fluctuations and the relationship between the static spin susceptibility and the in-plane fluctuation. It was found that three-dimensional ferromagnetic (FM) correlations are dominant and give rise to the FM ordering in CeRuPO. The out-of-plane fluctuations are significantly suppressed with increasing x, and it was revealed that the FM fluctuations become two dimensional near a FM quantum critical point (QCP). Our NMR results strongly suggest that a unique FM QCP in Ce(Ru1-xFex)PO is induced by the suppression of the magnetic correlations along the c-axis, which is a different mechanism from that presumed in heavy-fermion compounds.