Marie Curie is much more famous than her husband Pierre. But, Pierre Curie, who tragically died at age 46 by being hit by a horse-cart, was a brilliant scientist in his own right. One of his most notable discoveries concerns heat and magnetism and an effect that occurs in magnets at a temperature called the Curie Point.

How Magnets Work

The electromagnetic force is one of the four fundamental forces in the universe and magnetic fields are created at the atomic level by moving electric charges. The electric charge created by the moving electrons in atoms creates a tiny magnetic field. Each of these tiny atomic magnetic fields has a “direction” which is usually canceled out by other atoms with a field in another direction. That is because the direction of the magnetic field is random in most materials. However, in some materials, most notably iron, the direction of the magnetism is aligned and the material itself has a magnetic field in one direction because all the tiny magnetic fields reinforce each other.

In addition to ferrous materials that are naturally magnetic, magnetism can be created by running electricity through coiled wires.

The Curie Point

Pierre Curie discovered that all magnetic materials sharply lose their magnetic properties when heated to a specific temperature now called the “Curie Point” or “Curie Temperature.” For iron, this temperature is 1418 °F. This occurs because the heat causes movement of the substance’s atoms to a degree that it scrambles the unified direction of the magnetic field. Once the ferromagnetic substance cools down again it becomes magnetic.

For a fascinating demonstration of this, watch the short video below of a simple “Curie Point Magnetic Heat Engine.” Really cool.

IFOD on the Earth’s Magnetic Field and its periodic reversal.