Antiferromagnetic coupling of the single-molecule magnet Mn12 to a ferromagnetic substrate

TL;DR

This study uses density-functional theory to show that Mn12 single-molecule magnets prefer antiferromagnetic coupling when placed on a Ni(111) substrate, with superexchange interactions mediating the coupling.

Contribution

It demonstrates the magnetic coupling mechanism between Mn12 molecules and a ferromagnetic substrate using advanced computational methods.

Findings

Mn12 favors antiferromagnetic coupling to Ni(111)

Magnetic moments of Mn12 are altered when on Ni

Superexchange interactions via S, C, and O mediate coupling

Abstract

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.