Evidence of The Anomalous Fluctuating Magnetic State by Pressure Driven 4f Valence Change in EuNiGe$_3$

TL;DR

This study provides experimental evidence of pressure-induced valence fluctuations in EuNiGe3, revealing anomalous magnetic states and polarization effects in Eu ions, suggesting a complex intermediate valence and chiral spin-liquid-like behavior.

Contribution

It demonstrates direct observation of magnetic polarization in Eu3+ due to valence fluctuations under pressure, highlighting novel magnetic phenomena in EuNiGe3.

Findings

Magnetic polarization observed in Eu3+ and Eu2+ across pressure range

Transition from antiferromagnetic to fluctuating magnetic behavior

Enhanced Dzyaloshinskii-Moriya interactions leading to chiral spin-liquid-like states

Abstract

In rare-earth compounds with valence fluctuation, the proximity of the 4f level to the Fermi energy leads to instabilities of the charge configuration and the magnetic moment. Here, we provide direct experimental evidence for an induced magnetic polarization of the Eu$^{3+}$ atomic shell with J=0, due to intra-atomic exchange and spin-orbital coupling interactions with Eu$^{2+}$ atomic shell. By applying external pressure, a transition from antiferromagnetic to a fluctuating behavior in a EuNiGe$_3$ single crystals is probed. Magnetic polarization is observed for both valence states of Eu$^{2+}$ and Eu$^{3+}$ across the entire pressure range. The anomalous magnetism is discussed in terms of a homogeneous intermediate valence state where frustrated Dzyaloshinskii-Moriya couplings are enhanced by the onset of spin-orbital interaction and engender a chiral spin-liquid-like precursor.