M，W型六角钡铁氧体化学键性质和穆斯堡尔谱位移研究

Investigation of Chemical Bond Properties and MossbauerIsomer Shifts in M-, W- type Hexagonal Barium Ferrites

利用电介质的平均能带模型研究了M型、W型六角铁氧体的化学成键性质,计算了各晶位的共价性和穆斯堡尔同质异能位移,结果与实验值一致.确定了Fe2+在W型铁氧体中所占晶位.

By using the average band - gap model, chemical bond properties of M -, W - type hexagonal barium ferrites have been studied. Mossbauer isomer shifts of Fe-57 in BaFe12O19 and BaFe18O27 are calculated by using the chemical surrounding factor, h, definited by covalency 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 Fe2+ ions exist in 4f(3), site of W - type hexagonal barium ferrite. Special attention is given to the anisotropy of the bond susceptibilities of Fe-57 nuclei in 2b position. This theoretical method allows us to calculate accurately the bond structure and the isomer shifts of complex hexagonal ferrites.