Curiepunt

Curiepunt, or Curie temperature, is the temperature at which a ferromagnetic or ferrimagnetic material loses its permanent magnetization and becomes paramagnetic. It is named after Pierre Curie, who studied the magnetic properties of materials and identified the temperature at which spontaneous magnetization vanishes. The Curie point marks a magnetic phase transition driven by thermal agitation that overcomes the exchange interactions that align magnetic moments.

Below the Curie point, magnetic moments align to produce spontaneous magnetization even without an external field. Above the Curie point, thermal disorder destroys this long-range order and the material responds to magnetic fields only weakly, as a paramagnet. The susceptibility often follows the Curie–Weiss law, χ ≈ C/(T-θ), where θ is close to the Curie temperature.

Different ferromagnets have different Curie temperatures. For example, iron is around 770 °C, nickel around 358 °C, and cobalt around 1,115 °C. All else being equal, materials with higher exchange interaction retain magnetization to higher temperatures.

The Curie point is not the same as the melting point; it is a magnetic phase transition temperature. Knowledge of Tc is important for heat treatment, performance limits of magnets, and design of magnetic devices that operate at elevated temperatures. In some complex ferrimagnets, multiple ordering temperatures can occur, but the Curie point still denotes the transition to paramagnetism.