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

Abstract We investigated the electronic structure of layered Mn oxide Bi 3 Mn 4 O 12 (NO 3 ) with a Mn honeycomb lattice by x-ray absorption spectroscopy and model calculations. The valence of Mn was determined to be 4 + with a small charge-transfer energy of ∼ 1 eV. The values of ( J 1 , J 2 , J 3 , J c , J c 1 , and J c 2 ) obtained by unrestricted Hartree–Fock calculations on Mn 3 d –O 2 p lattice models show that intra-layer second and third neighbor superexchange interactions J 2 and J 3 as well as inter-layer superexchange interactions J c , J c 1 , and J c 2 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 J c 1 and antiferromagnetic J c 2 are responsible to the antiferromagnetic inter-layer coupling and that the intra-layer exchange interactions with the ferromagnetic J 2 and antiferromagnetic J 3 have no frustration effect.