View source for Physics:Hopkinson effect

{{Short description|Feature of ferromagnetic or ferrimagnetic materials}}
[[File:Magnetite Hopkinson peak.pdf|thumb|right|Thermomagnetic susceptibility curve for magnetite exhibiting a strong Hopkinson effect]]

The '''Hopkinson effect''' is a feature of [[Physics:Ferromagnetism|ferromagnetic]] or [[Physics:Ferrimagnetism|ferrimagnetic]] materials, in which an increase in [[Physics:Magnetic susceptibility|magnetic susceptibility]] is observed at temperatures between the [[Physics:Superparamagnetism#Blocking temperature|blocking temperature]] and the [[Physics:Curie temperature|Curie temperature]] of the material.  The Hopkinson effect can be observed as a peak in thermomagnetic curves that immediately precedes the susceptibility drop associated with the Curie temperature. It was first observed by John Hopkinson in 1889 in a study on iron.<ref>Hopkinson, John. “Magnetic and Other Physical Properties of Iron at a High Temperature”. Philosophical Transactions of the Royal Society of London. A 180 (1889): 443–465.</ref>

In single domain particles, a large Hopkinson peak results from a transient [[Physics:Superparamagnetism|superparamagnetic]] particle domain state.

==See also==
* {{annotated link|Physics:Ferroelectricity}}
* {{annotated link|Physics:Curie's law}}

== References ==
<references />

[[Category:Ferromagnetism]]

vi: Hiệu ứng Hopkinson

{{Sourceattribution|Hopkinson effect}}