Magnetic anisotropy and phononic properties of two-dimensional ferromagnetic Fe₃GeS₂ monolayer

In 2023, Fe₃GeS₂ monolayer with Curie temperature of 630 K is predicted, which is promising to be used in next-generation spintronic devices. However, its magnetic anisotropy and phononic properties are still unclear. In this paper, we implemented the first-principles calculations on Fe₃GeS₂ monolayer, and found its ferromagnetic ground state with robustness to the -1.5%-1.3% biaxial strain. Meanwhile, the out-of-plane magnetic anisotropy dominated by dipolar interaction is found in Fe₃GeS₂ monolayer. Finally, we studied the phononic properties to identify the dynamical stability of Fe₃GeS₂ monolayer and highlight the contribution from the anharmonic interaction of optical phonons to the thermal expansion coefficient. We also find two single-phonon modes can be used to design quantum mechanical resonators with a wide cool-temperature range. These results can provide a comprehensive understanding of the magnetism and phonon properties of two-dimensional (2D) Fe₃GeS₂, beneficial for the application of 2D Fe₃GeS₂ in spintronics.