Electronic and magnetic properties of polar magnets M2Mo3O8 (M = Mn, Fe, Co and Ni) from first principles studies

Through the first-principles density functional theory calculations, we systematically studied the electronic and magnetic properties of a series of polar magnets M2Mo3O8 (M = Mn, Fe, Co and Ni), which consists of alternative M-2 and Mo-3 two-dimensional honeycomb layers along the c axis. The electronic structural analysis indicate that the Mo ion exhibits 4+ oxidation state with 4d(2) electronic configuration. Owning to the formation of Mo-3 cluster, each small triangle with six electrons creates entirely filled molecular bonding states and completely empty an-tibonding states, giving rise to diamagnetic nature of Mo4+ ion. In nice agreement with the experimental ob-servations, the ferrimagnetic ordering, in which the interactions among the tetrahedal and octahedral M2+ sites (both intralayer and interlayer ones) are exclusively antiferromagnetic, is established for Mn2Mo3O8, while the C -type antiferromagnetic configuration, where the antiferromagentic M-2 honeycomb layers are ferromagnetic coupling along the c axis, is formed in M = Fe and Co case, nevertheless, the magnetic phase diagram of Ni2Mo3O8 is uncertain and complex, since all the magnetic orderings considered are almost degenerate within the limits of the calculated error. Furthermore, the variation of the electronic structures and magnetic properties were analyzed as occupation of 3d orbitals increasing from 3d(5) (Mn2+) to 3d(8) (Ni2+) in terms of the crystal field splitting and electronic correlation.