# Curie point

Curie point

The Curie point (Tc), or Curie temperature, is a term in physics and materials science, named after Pierre Curie (1859-1906), and refers to a characteristic property of a ferromagnetic or piezoelectric material.

Curie point in ferromagnetic materials

The Curie point of a ferromagnetic material is the temperature above which it loses its characteristic ferromagnetic ability (768°C for iron). At temperatures below the Curie point the magnetic moments are partially aligned within magnetic domains in ferromagnetic materials. As the temperature is increased towards the Curie point, the alignment (magnetization) within each domain decreases. Above the Curie point, the material is purely paramagnetic and there are no magnetized domains of aligned moments.

At temperatures above the Curie point, an applied magnetic field has a paramagnetic effect on the magnetization, but the combination of paramagnetism with ferromagnetism leads to the magnetization following a hysteresis curve with the applied field strength. The destruction of magnetization at the Curie temperature is a second-order phase transition and a critical point where the magnetic susceptibility is theoretically infinite.

One application of this effect is in magneto-optical storage media, where it is used for erasing and writing of new data. Famous examples include the Sony Minidisc format, as well as the defunct CD-MO format.

Other uses include temperature control in soldering irons such as the Weller WTCPT and, in general, where a temperature-controlled magnetization is desirable.

Curie temperature in piezoelectric materials

In analogy to ferromagnetic materials, the Curie temperature is also used in piezoelectric materials to describe the temperature above which the material loses its spontaneous polarization and piezoelectric characteristics. In lead zirconate titanate (PZT), the material is tetragonal below Tc and the unit cell contains a displaced central cation and hence a net dipole moment. Above Tc, the material is cubic and the central cation is no longer displaced from the centre of the unit cell. Hence, there is no net dipole moment and no spontaneous polarization.

Curie-Weiss law $k=C/\left(T-mbox\left\{Weiss constant\right\}\right)$

ee also

*See ferromagnetism for a list of ferromagnetic materials and their Curie temperatures.
* Ferroelectric effect
* Néel temperature

* [http://es.youtube.com/watch?v=X8ZHQQUusGo Ferromagnetic Curie Point] . Video by Walter Lewin, M.I.T.

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### Look at other dictionaries:

• Curie point — n. the temperature at which the magnetic properties of a substance change from ferromagnetic to paramagnetic, usually lower than the substance s melting point: also Curie temperature …   English World dictionary

• Curie point — Physics. the temperature beyond that at which a ferromagnetic substance exhibits paramagnetism. Also called Curie temperature. [1920 25; named after Pierre CURIE] * * * ▪ physics also called  Curie Temperature,         temperature at which… …   Universalium

• Curie point — noun the temperature above which a ferromagnetic substance loses its ferromagnetism and becomes paramagnetic • Syn: ↑Curie temperature • Hypernyms: ↑temperature * * * noun or curie temperature Usage: usually capitalized C …   Useful english dictionary

• Curie point — Kiuri taškas statusas T sritis fizika atitikmenys: angl. Curie point vok. Curie Punkt, m rus. точка Кюри, f pranc. point de Curie, m …   Fizikos terminų žodynas

• curie point — GLOSSARY OF VOLCANIC TERMS The temperature at which a body loses (by heating) or preserves (by cooling) its permanent magnetization. As rocks cool, the electromagnetic field aligns magnetic minerals in the magma, and their orientation is… …   Glossary of volcanic terms

• Curie point — Cu′rie point n. phs the temperature above which a ferromagnetic substance exhibits paramagnetism. Also called Cu′rie tem perature • Etymology: 1920–25; after Pierre Curie …   From formal English to slang

• Curie point — noun Date: 1911 1. the temperature at which there is a transition between the ferromagnetic and paramagnetic phases 2. a temperature at which the anomalies that characterize a ferroelectric substance disappear called also Curie temperature …   New Collegiate Dictionary

• curie point — /ˈkjuri pɔɪnt/ (say kyoohree poynt) noun the temperature at which a ferromagnetic substance becomes merely paramagnetic. {named in honour of Pierre Curie} …   Australian-English dictionary

• Curie point — Смотри температура Кюри …   Энциклопедический словарь по металлургии

• Curie point — Смотри точка Кюри …   Энциклопедический словарь по металлургии