Magnetic Surface on Nonmagnetic Bulk of Electride Hf2S

A recent experiment has reported the self-passivated electride Hf 2 S with excellent stability and continuous electrocatalytic ability [S. H. Kang et al., Sci. Adv. 2020, 6, eaba7416]. Starting from its 2H-type layered structure, we have studied the electronic, magnetic, and transport properties of the electride Hf 2 S in the monolayer and multilayer forms by combining first-principles electronic structure calculations and Kubo formula approach. Our calculations indicate that these thin films of Hf 2 S electride are both dynamically and thermodynamically stable. Astonishingly, the calculations further show that the outmost Hf atoms and the surface electron gas of the Hf 2 S multilayers are spin polarized, while the inner Hf atoms and the electron gas in the interlayer regions remain nonmagnetic. Due to the magnetic surface, the multilayer Hf 2 S exhibits many unusual transport properties such as the surface anomalous Hall effect and the electric-field-induced layer Hall effect. Our theoretical predictions on Hf 2 S call for future experimental verification.