Ferromagnetic Quantum Critical Point in FeGa3 Tuned by Mixed-Valence Fe Dimers

TL;DR

This study investigates the magnetic and electronic phase transition in Fe(Ga1-xGex)3, revealing a ferromagnetic quantum critical point driven by mixed-valence Fe dimers, with non-Fermi liquid behavior near critical doping.

Contribution

It demonstrates that mixed-valence Fe dimers in FeGa3 can be tuned to induce a ferromagnetic quantum critical point, a novel mechanism for quantum criticality in this material.

Findings

Identification of a ferromagnetic quantum critical point at x=0.052

Observation of non-Fermi liquid behavior near the critical point

Linking Fe dimer valence states to quantum criticality

Abstract

The magnetic, transport, and thermal properties of single crystals of the series Fe(Ga1-xGex)3 are reported. Pure FeGa3 is a nonmagnetic semiconductor, that when doped with small concentrations of Ge (extrinsic electrons), passes through an insulator-to-metal transition and displays non-Fermi liquid (NFL) behavior. Moreover, we observer clear signatures of a ferromagnetic quantum critical point (FM-QCP) in this system at x = 0.052. The mechanism of the local moment formation is consistent with a one-electron reduction of Fe dimer singlets, a unique structural feature in FeGa3, where the density of these mixed valence (Fe(III)-Fe(II)) dimers provides a unique tuning parameter of quantum criticality.