Anomalous resistivity upturn in the van der Waals ferromagnet Fe$_5$GeTe$_2$

TL;DR

This study investigates the low-temperature resistivity upturn in Fe$_5$GeTe$_2$, revealing that atomic disorder from the split Fe(1) site enhances electron-electron interactions and induces a Kondo effect, impacting its transport properties.

Contribution

It demonstrates how atomic structural disorder from the split Fe(1) site influences the low-temperature transport behavior in Fe$_5$GeTe$_2$, highlighting the role of electron-electron interactions and Kondo effect.

Findings

Resistivity upturn observed below 10 K.

Resistivity behavior explained by electron-electron interactions and Kondo effect.

Atomic disorder from split Fe(1) site affects transport properties.

Abstract

Fe$_5$GeTe$_2$ (n = 3, 4, 5) have recently attracted increasing attention due to their two-dimensional van der Waals characteristic and high temperature ferromagnetism, which make promises for spintronic devices. The Fe(1) split site is one important structural characteristic of Fe$_5$GeTe$_2$ which makes it very different from other Fe$_5$GeTe$_2$ (n = 3, 4) systems. The local atomic disorder and short-range order can be induced by the split site. In this work, the high-quality van der Waals ferromagnet Fe$_5$GeTe$_2$ were grown to study the low-temperature transport properties. We found a resistivity upturn below 10 K. The temperature and magnetic field dependence of the resistivity are in good agreement with a combination of the theory of disorder-enhanced three-dimensional electron-electron and single-channel Kondo effect. The Kondo effect exists only at low magnetic field B < 3 T, while electron-electron dominates the appearance for the low-temperature resistivity upturn. We believe that the enhanced three-dimensional electron-electron interaction in this system is induced by the local atomic structural disorder due to the split site of Fe(1). Our results indicate that the split site of Fe plays an important role for the exceptional transport properties.