Engineering the electronic structures and ferromagnetism of Fe2C monolayers via surface functionalization†

Abstract

To further advance the potential applications of Fe₂C monolayers in cutting-edge spintronic devices, the structural, electronic and magnetic properties of two-dimensional transition metal carbide Fe₂C were engineered via surface functionalization using the first-principles calculations. Results showed that all the symmetrically and asymmetrically functionalized Fe₂CTT′ (T, T′ = H, F, Cl, and Br) monolayers, except the Fe₂CFBr monolayer, were dynamically stable. They exhibited intrinsic ferromagnetism, high magnetic anisotropy energy and high spin polarization. Additionally, the Fe₂CH₂, Fe₂CHF, Fe₂CHCl, and Fe₂CHBr monolayers exhibited ferromagnetic metal properties, whereas Fe₂CCl₂ and Fe₂CClBr monolayers were half-metallic ferromagnets with 100% spin polarization. In particular, the Fe₂CF₂, Fe₂CBr₂ and Fe₂CFCl monolayers were classified as bipolar magnetic semiconductors (BMSs) owing to their distinctive band structures. In BMSs, fully spin-polarized currents could be generated and easily controlled, and the carrier's spin orientation could also be reversed by changing the sign of the applied gate voltage. Notably, the Curie temperatures of Fe₂CF₂ and Fe₂CFCl at 988 K and 995 K, respectively, were higher than that of the primitive monolayer Fe₂C. Thus, these results show that optimizing the Fe₂C monolayer via surface functionalization can improve the performance and extend its potential applications in the field of spintronics.