What is or does the Curie temperature measure?
The Curie temperature refers to the point at which materials lose their ferromagnetism, which in contrast refers to the ability to align their own atoms even in the absence of a magnetic field. In this case, a material becomes paramagnetic and requires an external magnetic field to re-magnetize and remain in that state. The phenomenon of Curie temperature was named after the scientist Pierre Curie. Magnetic materials can change their properties at a variety of temperatures, which often have to be quite high. When the temperature decreases again, the material regains its magnetism, illustrating that this phase change is reversible.