${\mathrm{Fe}}_{3-x}{\mathrm{GeTe}}_2$ is a layered van der Waals magnetic material with a relatively high ordering temperature and large anisotropy. While most studies have concluded the interlayer ordering to be ferromagnetic, there have also been reports of interlayer antiferromagnetism in ${\mathrm{Fe}}_{3-x}{\mathrm{GeTe}}_2$. Here, we investigate the interlayer magnetic ordering by neutron diffraction experiments, scanning tunneling microscopy (STM) and spin-polarized STM measurements, density functional theory plus U calculations, and STM simulations. We conclude that the layers of ${\mathrm{Fe}}_{3-x}{\mathrm{GeTe}}_2$ are coupled ferromagnetically and that in order to capture the magnetic and electronic properties of ${\mathrm{Fe}}_{3-x}{\mathrm{GeTe}}_2$ within density functional theory, Hubbard U corrections need to be taken into account.

• Received 1 June 2020
• Accepted 17 August 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.094403