Weyl-loop half-metal in Li3(FeO3)2

Nodal-line metals and semimetals, as interesting topological states of matter, have been mostly studied in nonmagnetic materials. Here, based on first-principles calculations and symmetry analysis, we predict that fully spin polarized Weyl loops can be realized in the half-metal state of the three-dimensional material Li3(FeO3)2. We show that this material has a ferromagnetic ground state, and it is a half-metal with only a single spin channel present near the Fermi level. The spin-up bands form two separate Weyl loops close to the Fermi level, which arise from band inversions and are protected by the glide mirror symmetry. One loop is type I, whereas the other loop is the hybrid type. Corresponding to these two loops in the bulk, on the (100) surface, there exist two fully spin polarized drumheads of surface states within the surface projections of the loops. The effects of the electron correlation and the spin-orbit coupling, as well as the possible hourglass Weyl chains in the nonmagnetic state, are discussed. The realization of fully spin polarized Weyl-loop fermions in the bulk and drumhead fermions on the surface for a half-metal may generate promising applications in spintronics.