  Two-dimensional (2D) intrinsic half-metallic materials are of great interest
to explore the exciting physics and applications of nanoscale spintronic
devices, but no such materials have been experimentally realized. Using
first-principles calculations based on density-functional theory (DFT), we
predicted that single-layer MnAsS$_4$ was a 2D intrinsic ferromagnetic (FM)
half-metal. The half-metallic spin gap for single-layer MnAsS$_4$ is about 1.46
eV, and it has a large spin splitting of about 0.49 eV in the conduction band.
Monte Carlo simulations predicted the Curie temperature (\emph{T}$_c$) was
about 740 K. Moreover, Within the biaxial strain ranging from -5\% to 5\%, the
FM half-metallic properties remain unchanged. Its ground-state with 100\%
spin-polarization ratio at Fermi level may be a promising candidate material
for 2D spintronic applications.
