Two-Dimensional Iron Silicide (FeSi_x) Alloys with Above-Room-Temperature Ferromagnetism

Two-dimensional (2D) materials with intrinsic room-temperature ferromagnetism have gathered tremendous interest as promising candidates for next-generation spintronics. Here, on the basis of first-principles calculations, we report a family of stable 2D iron silicide (FeSix) alloys via dimensional reduction of their bulk counterparts. Our results demonstrate that 2D Fe4Si2-hex, Fe4Si2-orth, Fe3Si2, and FeSi2 nanosheets are lattice-dynamically and thermally stable, confirmed by the calculated phonon spectra and Born-Oppenheimer dynamic simulation up to 1000 K. 2D FeSix nanosheets are ferromagnetic metals with estimated Curie temperatures ranging from 547 to 971 K due to strong direct exchange interaction between Fe sites. In addition, the electronic properties of 2D FeSix alloys can be maintained on silicon substrates, providing an ideal platform for spintronics applications in the nanoscale.