  Two-dimensional magnets have received increasing attention since Cr2Ge2Te6
and CrI3 were experimentally exfoliated and measured in 2017. Although layered
ferromagnetic metals were demonstrated at room temperature, a layered
ferromagnetic semiconductor with high Curie temperature (Tc) is yet to be
unveiled. Here, we theoretically predicted a family of high Tc ferromagnetic
monolayers, namely MnNX and CrCX (X=Cl, Br and I; C=S, Se and Te). Their Tc
values were predicted from over 100 K to near 500 K with Monte Carlo
simulations using an anisotropic Heisenberg model. Eight members among them
show semiconducting bandgaps varying from roughly 0.23 to 1.85 eV. These
semiconducting monolayers also show extremely large anisotropy, i.e. ~101 for
effective masses and ~102 for carrier mobilities, along the two in-plane
lattice directions of these layers. Additional orbital anisotropy leads to a
spin-locked linear dichroism, in different from previously known circular and
linear dichroisms in layered materials. Together with the mobility anisotropy,
it offers a spin-, dichroism- and mobility-anisotropy locking. These results
manifest the potential of this 2D family for both fundamental research and high
performance spin-dependent electronic and optoelectronic devices.
