Editing Coercivity (section)

==Experimental determination==
{| class="wikitable floatright"
|+ Coercivities of some magnetic materials
|-
! Material
! Coercivity<br />(kA/m)
|-
| [[Supermalloy]]<br />(16[[iron|Fe]]:79[[nickel|Ni]]:5[[molybdenum|Mo]])
| 0.0002<ref name=Tumanski>{{cite book|last1=Tumanski|first1=S.|title=Handbook of magnetic measurements|date=2011|publisher=CRC Press|location=Boca Raton, FL|isbn=9781439829523}}</ref>{{rp|131,133}}
|-
| [[Permalloy]] ([[iron|Fe]]:4[[nickel|Ni]])
| 0.0008–0.08<ref>{{Cite journal|title=Thickness and grain-size dependence of the coercivity in permalloy thin films|journal=Journal of Applied Physics|volume=81|issue=8|pages=4122|author=M. A. Akhter-D. J. Mapps-Y. Q. Ma Tan-Amanda Petford-Long-R. Doole|doi=10.1063/1.365100|year=1997|last2=Mapps|last3=Ma Tan|last4=Petford-Long|last5=Doole|bibcode=1997JAP....81.4122A}}</ref>
|-
| [[Iron filings]] (0.9995 [[mass fraction (chemistry)|wt]])
| 0.004–37.4<ref name="mysite.du.edu">{{Cite web |last=Calvert |first=J. B. |date=6 December 2003 |orig-date=13 December 2002 |title=Iron |url=http://mysite.du.edu/~jcalvert/phys/iron.htm |url-status=dead |archive-url=https://web.archive.org/web/20070915131344/http://mysite.du.edu/%7Ejcalvert/phys/iron.htm#Magn |archive-date=2007-09-15 |access-date=2023-11-04 |website=mysite.du.edu}}</ref><ref name="Magnetic Properties of Solids">{{cite web|url=http://hyperphysics.phy-astr.gsu.edu/Hbase/tables/magprop.html|title=Magnetic Properties of Solids|publisher=Hyperphysics.phy-astr.gsu.edu|access-date=22 November 2014}}</ref>
|-
| [[Electrical steel]] (11Fe:Si)
| 0.032–0.072<ref>{{cite web|url=http://cartech.ides.com/datasheet.aspx?E=193~192~191~190~189&CK=1967748|title=timeout|publisher=Cartech.ides.com|access-date=22 November 2014}}{{Dead link|date=July 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
|-
| [[Wrought iron|Raw iron]] (1896)
| 0.16<ref>{{cite book|url=https://books.google.com/books?id=G0cOAAAAYAAJ&pg=PA133|title=Dynamo-electric machinery|access-date=22 November 2014|last1=Thompson|first1=Silvanus Phillips|year=1896}}</ref>
|-
| [[Nickel]] (0.99 wt)
| 0.056–23<ref name="Magnetic Properties of Solids"/><ref>{{Cite journal|title=Influence of rf magnetron sputtering conditions on the magnetic, crystalline, and electrical properties of thin nickel films|journal=Journal of Applied Physics|volume=75|issue=10|pages=5779|author=M. S. Miller-F. E. Stageberg-Y. M. Chow-K. Rook-L. A. Heuer|doi=10.1063/1.355560|year=1994|last2=Stageberg|last3=Chow|last4=Rook|last5=Heuer|bibcode=1994JAP....75.5779M}}</ref>
|-
| [[Ferrite (magnet)|Ferrite]] magnet<br />(Zn<sub>x</sub>FeNi<sub>1−x</sub>O<sub>3</sub>)
| 1.2–16<ref>{{Cite journal|journal=IEEE Transactions on Magnetics|volume=33|issue=5|pages=3748–3750|doi=10.1109/20.619559|year=1997|last1=Zhenghong Qian|last2=Geng Wang|last3=Sivertsen|first3=J.M.|last4=Judy|first4=J.H.|title=Ni ''Zn'' ferrite thin films prepared by Facing Target Sputtering|bibcode=1997ITM....33.3748Q}}</ref>
|-
| 2Fe:Co,<ref>{{cite book|url=https://books.google.com/books?id=y0FF19lud5YC&pg=PA142|title=Handbook of Charged Particle Optics, Second Edition|access-date=22 November 2014|isbn=9781420045550|last1=Orloff|first1=Jon|date=2017-12-19|publisher=CRC Press }}</ref> iron pole
| 19<ref name="Magnetic Properties of Solids"/>
|-
| [[Cobalt]] (0.99 wt)
| 0.8–72<ref name="Pubs">{{Cite journal|title=Magnetic Cobalt Nanowire Thin Films|journal=The Journal of Physical Chemistry B|volume=109|issue=5|pages=1919–22|doi=10.1021/jp045554t|pmid=16851175|year=2005|last1=Luo|first1=Hongmei|last2=Wang|first2=Donghai|last3=He|first3=Jibao|last4=Lu|first4=Yunfeng}}</ref>
|-
| [[Alnico]]
| 30–150<ref>{{Cite web |title=Cast ALNICO Permanent Magnets |url=https://www.arnoldmagnetics.com/wp-content/uploads/2017/10/Cast-Alnico-Permanent-Magnet-Brochure-101117-1.pdf |access-date=4 November 2023 |website=Arnold Magnetic Technologies}}</ref>
|-
| Disk drive recording medium <br />([[chromium|Cr]]:[[cobalt|Co]]:[[platinum|Pt]])
| 140<ref>{{Cite journal|journal=IEEE Transactions on Magnetics|volume=27|issue=6|pages=5052–5054|doi=10.1109/20.278737|year=1991|last1=Yang|first1=M.M.|last2=Lambert|first2=S.E.|last3=Howard|first3=J.K.|last4=Hwang|first4=C.|title=Laminated CoPt ''Cr''/Cr films for low noise longitudinal recording|bibcode=1991ITM....27.5052Y}}</ref>
|-
| [[Neodymium magnet]] (NdFeB)
| 800–950<ref>{{Cite journal|title=High-remanence rapidly solidified Nd-Fe-B: Die-upset magnets (invited)|journal=Journal of Applied Physics|volume=73|issue=10|pages=5751|author=C. D. Fuerst-E. G. Brewer|doi=10.1063/1.353563|year=1993|last2=Brewer|bibcode=1993JAP....73.5751F}}</ref><ref>{{cite web|url=http://wondermagnet.com/magfaq.html|title=WONDERMAGNET.COM - NdFeB Magnets, Magnet Wire, Books, Weird Science, Needful Things|publisher=Wondermagnet.com|access-date=22 November 2014|archive-date=11 February 2015|archive-url=https://web.archive.org/web/20150211041455/http://www.wondermagnet.com/magfaq.html|url-status=dead}}</ref>
|-
| 12[[iron|Fe]]:13[[platinum|Pt]] ({{chem2|Fe48Pt52}})
| ≥980<ref>{{harvnb|Chen|Nikles|2002}}</ref>
|-
| <!--Someone with access plug in the proportions-->?([[dysprosium|Dy]],[[niobium|Nb]],[[gallium|Ga]]([[cobalt|Co]]):2[[neodymium|Nd]]:14[[iron|Fe]]:[[boron|B]])
| 2040–2090<ref>{{cite journal |last1=Bai |first1=G. |last2=Gao |first2=R.W. |last3=Sun |first3=Y. |last4=Han |first4=G.B. |last5=Wang |first5=B. |title=Study of high-coercivity sintered NdFeB magnets |journal=Journal of Magnetism and Magnetic Materials |date=January 2007 |volume=308 |issue=1 |pages=20–23 |doi=10.1016/j.jmmm.2006.04.029 |bibcode=2007JMMM..308...20B }}</ref><ref>{{cite journal |last1=Jiang |first1=H. |last2=Evans |first2=J. |last3=O’Shea |first3=M.J. |last4=Du |first4=Jianhua |title=Hard magnetic properties of rapidly annealed NdFeB thin films on Nb and V buffer layers |journal=Journal of Magnetism and Magnetic Materials |date=2001 |volume=224 |issue=3 |pages=233–240 |doi=10.1016/S0304-8853(01)00017-8 |bibcode=2001JMMM..224..233J }}</ref>
|-
| Samarium-cobalt magnet <br />(2[[samarium|Sm]]:17[[iron|Fe]]:3[[nitrogen|N]]; 10{{nbsp}}[[kelvin|K]])
| <40–2800<ref>{{cite journal |last1=Nakamura |first1=H. |last2=Kurihara |first2=K. |last3=Tatsuki |first3=T. |last4=Sugimoto |first4=S. |last5=Okada |first5=M. |last6=Homma |first6=M. |title=Phase Changes and Magnetic Properties of Sm 2 Fe 17 N x Alloys Heat-Treated in Hydrogen |journal=IEEE Translation Journal on Magnetics in Japan |date=October 1992 |volume=7 |issue=10 |pages=798–804 |doi=10.1109/TJMJ.1992.4565502 }}</ref><ref>{{cite journal |last1=Rani |first1=R. |last2=Hegde |first2=H. |last3=Navarathna |first3=A. |last4=Cadieu |first4=F. J. |title=High coercivity Sm 2 Fe 17 N x and related phases in sputtered film samples |journal=Journal of Applied Physics |date=15 May 1993 |volume=73 |issue=10 |pages=6023–6025 |id={{INIST|4841321}} |doi=10.1063/1.353457 |bibcode=1993JAP....73.6023R }}</ref>
|-
| [[Samarium–cobalt magnet|Samarium-cobalt magnet]]
| 3200<ref>{{Cite journal |last1=de Campos |first1=M. F. |last2=Landgraf |first2=F. J. G. |last3=Saito |first3=N. H. |last4=Romero |first4=S. A. |last5=Neiva |first5=A. C. |last6=Missell |first6=F. P. |last7=de Morais |first7=E. |last8=Gama |first8=S. |last9=Obrucheva |first9=E. V. |last10=Jalnin |first10=B. V. |date=1998-07-01 |title=Chemical composition and coercivity of SmCo5 magnets |url=https://pubs.aip.org/jap/article/84/1/368/491720/Chemical-composition-and-coercivity-of-SmCo5 |journal=Journal of Applied Physics |language=en |volume=84 |issue=1 |pages=368–373 |doi=10.1063/1.368075 |bibcode=1998JAP....84..368D |issn=0021-8979|url-access=subscription }}</ref>
|}

Typically the coercivity of a magnetic material is determined by measurement of the [[magnetic hysteresis]] loop, also called the ''magnetization curve'', as illustrated in the figure above. The apparatus used to acquire the data is typically a [[vibrating-sample magnetometer|vibrating-sample]] or alternating-gradient [[magnetometer]]. The applied field where the data line crosses zero is the coercivity. If an [[antiferromagnet]] is present in the sample, the coercivities measured in increasing and decreasing fields may be unequal as a result of the [[exchange bias]] effect.{{citation needed|date=January 2021}}

The coercivity of a material depends on the time scale over which a magnetization curve is measured.  The magnetization of a material measured at an applied reversed field which is nominally smaller than the coercivity may, over a long time scale, slowly [[Relaxation (physics)|relax]] to zero.  Relaxation occurs when reversal of magnetization by domain wall motion is [[Arrhenius equation|thermally activated]] and is dominated by [[magnetic viscosity]].<ref>{{harvnb|Gaunt|1986}}</ref> The increasing value of coercivity at high frequencies is a serious obstacle to the increase of [[Bit rate|data rates]] in high-[[bandwidth (computing)|bandwidth]] magnetic recording, compounded by the fact that increased storage density typically requires a higher coercivity in the media.{{Citation needed|date=September 2010}}