Strong anisotropy and magnetostriction in the two-dimensional Stoner ferromagnetFe3GeTe2

Computationally characterizing magnetic properies of novel two-dimensional (2D) materials serves as an important first step of exploring possible applications. Using density-functional theory, we show that single-layer ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ is a potential 2D material with sufficiently low formation energy to be synthesized by mechanical exfoliation from the bulk phase with a van der Waals layered structure. In addition, we calculated the phonon dispersion demonstrating that single-layer ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ is dynamically stable. Furthermore, we find that similar to the bulk phase, 2D ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ exhibits a magnetic moment that originates from a Stoner instability. In contrast to other 2D materials, we find that single-layer ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ exhibits a significant uniaxial magnetocrystalline anisotropy energy of $920\ensuremath{\mu}\mathrm{eV}$ per Fe atom originating from spin-orbit coupling. Finally, we show that applying biaxial tensile strains enhances the anisotropy energy, which reveals strong magnetostriction in single-layer ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ with a sizable magneostrictive coefficient. Our results indicate that single-layer ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ is potentially useful for magnetic storage applications.