Abstract: By using the average band-gap model, chemical bond properties of BaTi₂Fe₄O₁₁ and
BaSn₂Fe₄O₁₁ were studied. Mossbauer isomer shifts of ⁵⁷Fe, ¹¹⁹Sn in BaTi₂Fe₄O₁₁ and BaSn₂Fe₄O₁₁ were calculated by using the chemical surrounding factor, h, defined by covalency and electronic polarizability. The charge state and site of
⁵⁷Fe and ¹¹⁹Sn were also represented. The calculated results show that the covalency of 2a, 4f, 4e, 6g sites in BaTi₂Fe₄O₁₁
is 0.062,0.354,0.309,0.361 respectively and one of 2a, 4f, 4e, 6g sites in BaSn₂Fe₄O₁₁ is 0.062, 0.353, 0.183, 0.255 respectively.

Key words: R-type hexagonal ferrite, chemical bond, mossbauer spectroscopy