Impact of Mn–O–O–Mn superexchange pathways in a honeycomb lattice Mn oxide with small charge-transfer energy

••The electronic state of Bi3Mn4O12(NO3) was studied by x-ray absorption spectroscopy.••The values of magnetic interactions were obtained by Hartree–Fock calculations.••The superexchange interactions are enhanced due to Mn–O–O–Mn pathways.

We investigated the electronic structure of layered Mn oxide Bi3Mn4O12(NO3) with a Mn honeycomb lattice by x-ray absorption spectroscopy and model calculations. The valence of Mn was determined to be 4+4+ with a small charge-transfer energy of ∼∼ 1 eV. The values of (J1, J2, J3, Jc, Jc1, and Jc2) obtained by unrestricted Hartree–Fock calculations on Mn 3d–O 2p lattice models show that intra-layer second and third neighbor superexchange interactions J2 and J3 as well as inter-layer superexchange interactions Jc, Jc1, and Jc2 are enhanced due to Mn–O–O–Mn pathways, which are activated by the smallness of charge-transfer energy. The present analysis indicates that the ferromagnetic Jc1 and antiferromagnetic Jc2 are responsible to the antiferromagnetic inter-layer coupling and that the intra-layer exchange interactions with the ferromagnetic J2 and antiferromagnetic J3 have no frustration effect.