Barium ferrite

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(O2-)4. The Fe3+ centers, with a high-spin d5 configuration, are ferromagnetically coupled. [cite book | author = Shriver, D. F.; Atkins, P. W.; Overton, T. L.; Rourke, J. P.; Weller, M. T.; Armstrong, F. A. | title = Inorganic Chemistry | publisher = W. H. Freeman | location = New York | year = 2006 | isbn = 0-7167-4878-9] This area of technology is usually considered to be an application of the related fields of materials science and solid state chemistry. It is also used in subwoofer magnets to provide power.

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. [cite journal
author = Y. Goto, T. Takada
title = Phase Diagram of the System BaO-Fe2O3
journal = Journal of the American Ceramic Society
year = 1960
volume = 43
issue = 3
pages = 150–153
doi = 10.1111/j.1151-2916.1960.tb14330.x ] Thus, BaFe12O19 is related to Fe12O20, with the empirical formula Fe3O4, i.e. magnetite. [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.]

Barium ferrites are robust ceramics that are generally stable to moisture and corrosion-resistant. [cite journal
author = C. Okazaki, S. Mori, F. Kanamaru
title = Magnetic and Crystallographical Properties of Hexagonal Barium Mono-Ferrite, BaO·Fe2O3
journal = Journal of the Physical Society of Japan
year = 1961
volume = 16
issue = 3
pages = 119–119
doi = 10.1143/JPSJ.16.119
url = http://jpsj.ipap.jp/link?JPSJ/16/119/ ]

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