Editing Coercivity (section)

==Definitions==

[[File:Coercivities in B-H curve.svg|thumb|Graphical definition of different coercivities in flux-vs-field hysteresis curve (B-H curve), for a hypothetical hard magnetic material.]]
[[File:Coercivities in M-H curve.svg|thumb|Equivalent definitions for coercivities in terms of the magnetization-vs-field (M-H) curve, for the same magnet.]]

Coercivity in a [[ferromagnet|ferromagnetic material]] is the intensity of the applied [[magnetic field]] (''H'' field) required to demagnetize that material, after the magnetization of the sample has been driven to [[saturation (magnetic)|saturation]] by a strong field. This demagnetizing field is applied opposite to the original saturating field. There are however different definitions of coercivity, depending on what counts as 'demagnetized', thus the bare term "coercivity" may be ambiguous:

* The ''normal coercivity'', {{math|''H''<sub>Cn</sub>}}, is the ''H'' field required to reduce the [[magnetic flux]] (average ''B'' field inside the material) to zero.
* The ''intrinsic coercivity'', {{math|''H''<sub>Ci</sub>}}, is the ''H'' field required to reduce the [[magnetization]] (average ''M'' field inside the material) to zero.
* The ''remanence coercivity'', {{math|''H''<sub>Cr</sub>}}, is the ''H'' field required to reduce the [[remanence]] to zero, meaning that when the ''H'' field is finally returned to zero, then both ''B'' and ''M'' also fall to zero (the material reaches the origin in the hysteresis curve).<ref name="Bertotti1998">{{cite book|author=Giorgio Bertotti|title=Hysteresis in Magnetism: For Physicists, Materials Scientists, and Engineers|url=https://books.google.com/books?id=ybVQAwAAQBAJ|date=21 May 1998|publisher=Elsevier Science|isbn=978-0-08-053437-4}}</ref>

The distinction between the normal and intrinsic coercivity is negligible in soft magnetic materials, however it can be significant in hard magnetic materials.<ref name="Bertotti1998"/> The strongest [[rare-earth magnet]]s lose almost none of the magnetization at ''H''<sub>Cn</sub>.