  Two-dimensional Cr2N MXene as well as the surface-passivated Cr2NF2,
Cr2N(OH)2 and Cr2NO2 are investigated by using density functional theory. The
Cr2N is an anti-ferromagnetic metal. The F atom or OH group-passivation does
not change the anti-ferromagnetic characteristics. However, Cr2NO2 has a
ferromagnetic ground state, which is a half-metal. The half-metallicity of
Cr2NO2 is still robust when bias is applied to the nanometer sized device. The
half-metallicity is intrinsic and does not require atomically clean surfaces.
Therefore the stable surface-oxygen-passivated MXene is a good candidate for
spintronics.
