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 (FeSi x ) alloys via dimensional reduction of their bulk counterparts. Our results demonstrate that 2D Fe 4 Si 2 -hex, Fe 4 Si 2 -orth, Fe 3 Si 2 , and FeSi 2 nanosheets are lattice-dynamically and thermally stable, confirmed by the calculated phonon spectra and Born-Oppenheimer dynamic simulation up to 1000 K. 2D FeSi x 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 FeSi x alloys can be maintained on silicon substrates, providing an ideal platform for spintronics applications in the nanoscale.