Metamagnetic Behavior and Kondo Breakdown in Heavy-Fermion CeFePO

TL;DR

This study reveals metamagnetic behavior and Kondo breakdown in CeFePO, a heavy-fermion compound, showing critical behavior around a specific magnetic field linked to Fermi-surface instability and local Kondo singlet breaking.

Contribution

It demonstrates the first observation of metamagnetism and Kondo breakdown in CeFePO, highlighting a new magnetic field-driven quantum critical phenomenon in this material.

Findings

Metamagnetic transition at H_M ≈ 4 T perpendicular to c-axis.

Critical behavior associated with Kondo breakdown.

H_M proportional to inverse effective mass and susceptibility peak temperature.

Abstract

We report that nonmagnetic heavy-fermion (HF) iron oxypnictide CeFePO with two-dimensional XY-type anisotropy shows a metamagnetic behavior at the metamagnetic field H_M \simeq 4 T perpendicular to the c-axis and that a critical behavior is observed around H_M. Although the magnetic character is entirely different from that in other Ce-based HF metamagnets, H_M in these metamagnets is linearly proportional to the inverse of the effective mass, or to the temperature where the susceptibility shows a peak. This finding suggests that H_M is a magnetic field breaking the local Kondo singlet, and the critical behavior around H_M is driven by the Kondo breakdown accompanied by the Fermi-surface instability.