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

Abstract

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 M2 and Mo3 two-dimensional honeycomb layers along the c axis. The electronic structural analysis indicate that the Mo ion exhibits 4+ oxidation state with 4d2 electronic configuration. Owning to the formation of Mo3 cluster, each small triangle with six electrons creates entirely filled molecular bonding states and completely empty antibonding states, giving rise to diamagnetic nature of Mo4+ ion. In nice agreement with the experimental observations, 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 M2 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 3d5 (Mn2+) to 3d8 (Ni2+) in terms of the crystal field splitting and electronic correlation.