Editing Ferromagnetism (section)

==Terms==
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| image1   = Ferromagnetic ordering.svg
| caption1 = Ferromagnetic material: all the molecular magnetic dipoles are pointed in the same direction
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| image2   = Ferrimagnetic ordering.svg
| caption2 = Ferrimagnetic material: some of the dipoles point in the opposite direction, but their smaller contribution is overcome by the others
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Historically, the term ''ferromagnetism'' was used for any material that could exhibit [[spontaneous magnetization]]: a net magnetic moment in the absence of an external magnetic field; that is, any material that could become a [[magnet]]. This definition is still in common use.<ref>{{cite book |editor-last1=Somasundaran |editor-first1=P. |title=Encyclopedia of surface and colloid science |date=2006 |publisher=Taylor & Francis |location=New York |isbn=978-0-8493-9608-3 |page=3471 |edition=2nd}}</ref>

In a landmark paper in 1948, [[Louis Néel]] showed that two levels of magnetic alignment result in this behavior. One is ferromagnetism in the strict sense, where all the magnetic moments are aligned. The other is ''[[ferrimagnetism]]'', where some magnetic moments point in the opposite direction but have a smaller contribution, so spontaneous magnetization is present.<ref>{{cite book |last1=Cullity |first1=B.&nbsp;D. |last2=Graham |first2=C.&nbsp;D. |chapter=6. Ferrimagnetism |title=Introduction to Magnetic Materials |date=2011 |publisher=John Wiley & Sons |isbn=978-1-118-21149-6}}</ref><ref>{{cite book |last1=Aharoni |first1=Amikam |title=Introduction to the theory of ferromagnetism |date=2000 |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-850809-0 |edition=2nd}}</ref>{{rp|28–29}}

In the special case where the opposing moments balance completely, the alignment is known as ''[[antiferromagnetism]]''; antiferromagnets do not have a spontaneous magnetization.
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