Barium ferrite

Barium ferrite, abbreviated BaFe, is the chemical compound with the formula BaFe₂O₄. This and related ferrite materials are components in magnetic stripe cards. BaFe is described as Ba²⁺(Fe³⁺)₂(O^2-)₄. The Fe³⁺ centers, with a high-spin d⁵ configuration, are ferromagnetically coupled.^[1] This area of technology is usually considered to be an application of the related fields of materials science and solid state chemistry.

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A related family of industrially useful "hexagonal ferrites" are known, also containing barium. In contrast to the usual spinel structure, these materials feature hexagonally close-packed framework of oxides. Furthermore some the oxygen centers are replaced by Ba²⁺ ions. Formulas for these species include BaFe₁₂O₁₉, BaFe₁₅O₂₃, and BaFe₁₈O₂₇.^[2] Thus, BaFe₁₂O₁₉ is related to Fe₁₂O₂₀, with the empirical formula Fe₃O₄, i.e. magnetite.^[3]

Barium ferrites are robust ceramics that are generally stable to moisture and corrosion-resistant.^[4]

References

1. ^ Shriver, D. F.; Atkins, P. W.; Overton, T. L.; Rourke, J. P.; Weller, M. T.; Armstrong, F. A. (2006). Inorganic Chemistry. New York: W. H. Freeman. ISBN 0-7167-4878-9. 
2. ^ Y. Goto, T. Takada (1960). "Phase Diagram of the System BaO-Fe₂O₃". Journal of the American Ceramic Society 43 (3): 150-153. doi:10.1111/j.1151-2916.1960.tb14330.x.
3. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
4. ^ C. Okazaki, S. Mori, F. Kanamaru (1961). "Magnetic and Crystallographical Properties of Hexagonal Barium Mono-Ferrite, BaO·Fe₂O₃". Journal of the Physical Society of Japan 16 (3): 119-119. doi:10.1143/JPSJ.16.119.