Nonmagnetic ground state of marcasite FeTe$_{2}$: The competition between crystal field splitting and on-site Coulomb repulsion

TL;DR

This study uses first-principles calculations and microscopy to reveal that the nonmagnetic ground state of marcasite FeTe₂ results from a competition between crystal field splitting and Coulomb repulsion, explaining its anomalous magnetic behavior.

Contribution

It introduces a simple competing mechanism involving crystal field splitting and Coulomb repulsion to determine the magnetic ground state in localized-moment crystalline systems.

Findings

Bulk FeTe₂ is nonmagnetic at ground state.

Surface Fe atoms exhibit magnetic responses at low temperature.

Competition between crystal field and Coulomb repulsion influences magnetism.

Abstract

The magnetic ground states in crystalline systems are significant for both fundamental condensed matter physics and practical materials engineering. Marcasite FeTe$_{2}$, characterized as a small-gap semiconductor, exhibits anomalous magnetic behaviors in low-temperature experiments. In this study, first-principles density functional theory calculations combined with scanning tunneling microscopy/spectroscopy are employed to investigate the magnetic ground state of marcasite FeTe$_{2}$. It is revealed that the competition between crystal field splitting and on-site Coulomb repulsion plays the key role in the formation of localized magnetic moments in FeTe$_{2}$. The ground state of FeTe$_{2}$ bulk is confirmed to be nonmagnetic, while the magnetic responses of FeTe$_{2}$ observed at low temperature are suggested to be related to the magnetic Fe atoms on the crystal surfaces. Our work proposes a straightforward competing mechanism for determining ground-state magnetism of various localized-moment crystalline systems.