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 eg 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 t2g states that leads to the unusual situation that the ferromagnetic phase is more stable than most antiferromagnetic configurations.
Bibliographical noteFunding Information:
J.L. gratefully acknowledges financial support from “One-hundred Talent Plan” of the Chinese Academy of Sciences. This work is supported by the National Basic Research Program of China (973 Program) Grant No. G2009CB929300 and the National Natural Science foundation of China under Grant Nos. 60521001 and 6077061. The work at NREL is supported by the U.S. DOE under Contract No. DE-AC36-08GO28308.