In physics, the Curie point is the temperature above which a ferromagnet loses its ferromagnetic ability to possess a net (spontaneous) magnetization in the absence of an external magnetic field. At temperatures below the Curie point, magnetic moments are partially aligned within magnetic domains in ferromagnetic materials. As the Curie point is approached, thermal fluctuations increasingly destroy this alignment, until the net magnetization becomes zero at and above the Curie point. Above the Curie point, the material is purely paramagnetic.
Below 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 Curie temperature is a second-order phase transition and a critical point where the magnetic susceptibility is theoretically infinite.
There are four magnetic elements: iron, nickel, cobalt, and gadolinium. The first three elements have Curie points above 500 C. The rare earth element gadolinium has a Curie Point of 16 C.
The effect is used for temperature control in soldering irons.
The Curie point is named after Pierre Curie (1859-1906).
See also: Ferroelectric effect