Magnetic ground state and electron-doping tuning of Curie temperature in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>GeTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> : First-principles studies

Intrinsic magnetic van der Waals (vdW) materials have attracted much attention, especially ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ (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 exchange interactions in FGT frustrated, our Monte Carlo simulations agree with total energy calculations, confirming ground state is indeed ferromagnetic (FM). confirm Curie temperature raising under electron doping an intrinsic effect. A tiny reduces frustration, resulting significant increase temperature. also calculate spin-wave dispersion, small spin gap as well nearly flat band magnon spectra. These features can compared future neutron scattering measurement finally clarify microscopic mechanism these two-dimensional family materials.