关键词: 铁氧体, 化学键, 穆斯堡尔谱法

By using the average band-gap model, chemical bond properties of M-, W-type hexagonal barium ferrites have been studied. Mossbauer isomer shifts of^57 Fe in BaFe12O19 and BaFe18O27 are calculated by using the chemical surrounding factor, h, definited bycovalency and electronic polarizability. The calculation results of the Mossbauer isomer shifts in various crystallographic positions are in agreement with their experimental values. It is verified that the Fe^2+ ions exist in 4f3, site of W- type hexagonal barium ferrite. Special attention is given to the anisotropy of the bond susceptibilities of^57 Fe nuclei in 2b position. This theoretical method allows us to calculate accurately the bond structure and the isomer shifts of complex hexagonal ferrites.

Key words: FERRITE, CHEMICAL BONDS, MOSSBAUER SPECTROMETRY