Origin of antiferromagnetism in CoO: A density functional theory study

We have investigated the origin of antiferromagnetism of CoO in the rocksalt structure using spin-polarized density functional theory calculations. We find that in the rocksalt structure, the superexchange interaction between the occupied and unoccupied e(g) states plays the dominant role, which leads to an antiferromagnetic ground state, but the system also has a strong direct exchange interaction between the partially occupied minority spin t(2g) states that leads to the unusual situation that the ferromagnetic phase is more stable than most antiferromagnetic configurations.