Orbital Design of Two-Dimensional Transition-Metal Peroxide Kagome Crystals with Anionogenic Dirac Half-Metallicity.

Assembling p orbital ferromagnetic half-metallicity and a topological element, such as a Dirac point at the Fermi level, in a single nanomaterial is of particular interest for long-distance, high-speed, and spin-coherent transportation in nanoscale spintronic devices. On the basis of the tight-binding model, we present an orbital design of a two-dimensional (2D) anionogenic Dirac half-metal (ADHM) by patterning cations with empty d orbitals and anions with partially filled p-type orbitals into a kagome lattice. Our first-principles calculations show that 2D transition-metal peroxides TM(O) (TMO, TM = Ti, Zr, Hf), containing group IVB transition-metal cations [TM] bridged with dioxygen anions [O] in a kagome structure, are stable ADHMs with a Curie temperature over 103 K. The 2/3 filled π* orbitals of dioxygen anions are ferromagnetically coupled, leading to p orbital ferromagnetism and a half-metallic Dirac point right at the Fermi level with a Fermi velocity reaching 2.84 × 10 m/s. We proposed that 2D TM(O) crystals may be extracted from ABO bulk materials containing 2D TMO layers.