First-principle study of the electronic structures and optical properties of six typical hexaferrites

The structural, electronic and optical properties of hexagonal ferrites MFe 12 O 19 (M = Sr, Ba, Pb, Sr 0.5 Ba 0.5 , Sr 0.5 Pb 0.5 and Ba 0.5 Pb 0.5 ) are calculated by plane-wave pseudopotential density functional theory with general gradient approximation (GGA) and GGA+ U . The calculated lattice constants and band gaps are in good agreement with the available experimental and theoretical values. Lattice constants change corresponding to the cation radii at M-sites. The electronic structure shows that all the six hexaferrites are narrow gap semiconductors and Sr 2+ and Ba 2+ at M-sites have little contribution to the DOS at the vicinity of Fermi level due to the ionic bond interaction nature between M 2+ and O 2− . It should be noted that for Pb 2+ , comparing with the narrow localized s-states of Sr 2+ and Ba 2+ , there is a significant broadening of its s -states from −7 eV to the Fermi level, indicating its minority donation to the valence band near E f . The six MFOs (FO refers Fe 12 O 19 ) could be classified into two categories: Pb-containing hexaferrites (PFO, SPFO and BPFO) and others (SFO, BFO and SBFO). The former has larger static dielectric constants. This study will serve as the base for the investigation of the correlation among factors such as site preferences, properties and substitution strategies for MFOs.