Transition-Metal Dihydride Monolayers: A New Family of Two-Dimensional Ferromagnetic Materials with Intrinsic Room-Temperature Half-Metallicity

Two-dimensional (2D) ferromagnetic materials with intrinsic half-metallicity are highly desirable for nanoscale spintronic applications. Here, we predict a new and stable family of 2D transition-metal dihydride (MH₂; M = Sc, Ti, V, Cr, Fe, Co, Ni) monolayers with novel properties. Our density functional theory computation shows that CoH₂ and ScH₂ monolayers are ferromagnetic metals, while the others are antiferromagnetic semiconductors. In particular, the CoH₂ monolayer is a perfect half-metal with a wide spin gap of 3.48 eV. The ScH₂ monolayer can also possess half-metallicity through hole doping. Most importantly, our Monte Carlo simulations show that the CoH₂ monolayer possesses an above-room-temperature Curie point (339 K), while that of the ScH₂ monolayer can also reach 160 K. A synthetic approach is proposed to realize CoH₂ and ScH₂ monolayers in the laboratory. Notably, their half-metallicity can be well maintained on substrates. The new family of MH₂ monolayers are promising functional materials for spintronic applications due to their novel magnetic properties.