  Two-dimensional ferromagnetic (2D FM) half-metal holds great potential for
quantum magnetoelectronics and spintronic devices. Here, using density
functional calculations and magnetic pictures, we study the electronic
structure and magnetic properties of the novel van der Waals (vdW)
metal-organic framework (MOF), CrCl2(N2C4H4)2, i.e. CrCl2(pyrazine)2. Our
results show that CrCl2(pyrazine)2 is a 2D FM half-metal, having a strong
intralayer FM coupling but a much weak interlayer one due to the vdW spacing.
Its spin-polarized conduction bands are formed by the pyrazine molecular
orbitals and are polarized by the robust Cr3+ local spin = 3/2. These results
agree with the recent experiments [Pedersen et al., Nature Chemistry, 2018, 10,
1056]. More interestingly, CrCl2(pyrazine)2 monolayer has a strong doping
tunability of the FM half-metallicity, and the FM coupling would be
significantly enhanced by electron doping. Our work highlights a vital role of
the organic ligand and suggests that vdW MOF is also worth exploration for new
2D magnetic materials.
