Magnetic ground state and electron doping tuning of Curie temperature in Fe$_3$GeTe$_2$: first-principles studies

TL;DR

This study uses first-principles calculations to analyze the magnetic properties of Fe$_3$GeTe$_2$, revealing how electron doping can enhance its Curie temperature and detailing its magnetic excitation spectrum.

Contribution

It provides a comprehensive first-principles analysis of both bulk and monolayer Fe$_3$GeTe$_2$, clarifying the magnetic ground state and effects of electron doping on Curie temperature.

Findings

Bulk FGT has a ferromagnetic ground state.

Tiny electron doping significantly increases Curie temperature.

Magnon spectra show a small spin gap and flat band.

Abstract

Intrinsic magnetic van der Waals (vdW) materials have attracted much attention, especially Fe$_{3}$GeTe$_{2}$ (FGT), which exhibits highly tunable properties. However, despite vast efforts, there are still several challenging issues to be resolved. Here using a first-principles linear-response approach, we carry out comprehensive investigation of both bulk and monolayer FGT. We find that although the magnetic exchange interactions in FGT are frustrated, our Monte Carlo simulations agree with the total energy calculations, confirming that the ground state of bulk FGT is indeed ferromagnetic (FM). A tiny electron doping reduces the magnetic frustration, resulting in significant increasing of the Curie temperature. We also calculate the spin-wave dispersion, and find a small spin gap as well as a nearly flat band in the magnon spectra. These features can be used to compare with the future neutron scattering measurement and finally clarify the microscopic magnetic mechanism in this two-dimensional family materials.