  Exploring two-dimensional (2D) magnetic semiconductors with room temperature
magnetic ordering and electrically controllable spin polarization is a highly
desirable but challenging task for nanospintronics. Here, through first
principles calculations, we propose to realize such a material by exfoliating
the recently synthesized organometallic layered crystal
Li$_{0.7}$[Cr(pyz)$_2$]Cl$_{0.7}$0.25$\cdot$(THF) (pyz = pyrazine, THF =
tetrahydrofuran) [Science 370, 587 (2020)]. The feasibility of exfoliation is
confirmed by the rather low exfoliation energy of 0.27 J/m$^2$, even smaller
than that of graphite. In exfoliated Cr(pyz)$_2$ monolayer, each pyrazine ring
grabs one electron from the Cr atom to become a radical anion, then a strong
$d$-$p$ direct exchange magnetic interaction emerges between Cr cations and
pyrazine radicals, resulting in room temperature ferrimagnetism with a Curie
temperature of 342 K. Moreover, Cr(pyz)$_2$ monolayer is revealed to be an
intrinsic bipolar magnetic semiconductor where electrical doping can induce
half-metallic conduction with controllable spin-polarization direction.
