  We investigate magnetic coupling between a monolayer of prototype
single-molecule magnets Mn12 and a ferromagnetic Ni(111) substrate through S,
using density-functional theory (DFT) and a DFT+U method. Our DFT and DFT+U
calculations show that the Mn12 molecules favor antiferromagnetic coupling to
the Ni substrate, and that they possess magnetic moments deviated from the
magnetic moments of isolated Mn12 molecules. We find that the magnetic easy
axis of the Mn12 on Ni (whole system) is dictated by that of the Ni substrate.
The antiferromagnetic coupling is, dominantly, caused by superexchange
interactions between the magnetic moments of the Mn and the Ni substrate via
the S, C, and O anions. Our findings can be observed from x-ray magnetic
circular dichroism or scanning tunneling microscopy.
