Barium ferrite
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2008-05-28T08:03:21Z
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'''Barium ferrite''', abbreviated BaFe, is the [[chemical compound]] with the [[chemical formula|formula]] BaFe<sub>2</sub>O<sub>4</sub>. This and related [[Ferrite (iron)|ferrite]] materials are components in [[magnetic stripe card]]s. BaFe is described as Ba<sup>2+</sup>(Fe<sup>3+</sup>)<sub>2</sub>(O<sup>2-</sup>)<sub>4</sub>. The Fe<sup>3+</sup> centers, with a [[Crystal field theory|high-spin]] d<sup>5</sup> configuration, are [[ferromagnetism|ferromagnetic]]ally coupled.<ref>{{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}}</ref> 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 Ba<sup>2+</sup> ions. Formulas for these species include BaFe<sub>12</sub>O<sub>19</sub>, BaFe<sub>15</sub>O<sub>23</sub>, and BaFe<sub>18</sub>O<sub>27</sub>.<ref>{{cite journal
| author = Y. Goto, T. Takada
| title = Phase Diagram of the System BaO-Fe<sub>2</sub>O<sub>3</sub>
| 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 }}
</ref> Thus, BaFe<sub>12</sub>O<sub>19</sub> is related to Fe<sub>12</sub>O<sub>20</sub>, with the empirical formula Fe<sub>3</sub>O<sub>4</sub>, i.e. [[magnetite]].<ref>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.</ref>
Barium ferrites are robust [[ceramic]]s that are generally stable to moisture and corrosion-resistant.<ref>{{cite journal
| author = C. Okazaki, S. Mori, F. Kanamaru
| title = Magnetic and Crystallographical Properties of Hexagonal Barium Mono-Ferrite, BaO·Fe<sub>2</sub>O<sub>3</sub>
| 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/ }}
</ref>
==References==
<references/>
[[Category:Barium compounds]]
[[Category:Iron compounds]]
[[Category:oxides]]
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[[ar:فيريت باريوم]]