Ferromagnetism refers to the magnetic state of a material and has the phenomenon of spontaneous magnetization. Among the materials, iron is the most widely known, hence its name.

After some materials are magnetized under the action of an external magnetic field, even if the external magnetic field disappears, they can still maintain their magnetized state and have magnetic properties, so-called spontaneous magnetization. All magnets are ferromagnetic or ferrimagnetic.

Basically the concept of ferromagnetism includes any substance that exhibits magnetic properties in the absence of an external magnetic field. This concept is still used today. But with a deeper understanding of different display magnetic materials and their magnetism, scholars have better defined this concept. A substance is said to be ferromagnetic when all its magnetic ions in its original cell point in its magnetic direction. If the magnetic field of only part of the ions points in its magnetic direction, it is called ferrimagnetism. If the directions pointed by their magnetic ions exactly cancel each other out (although all magnetic ions point in two opposite directions), it is called antiferromagnetism.

There is a critical temperature for the magnetic phenomenon of matter, and only at this temperature. For ferromagnetic and ferrimagnetic materials, this temperature is called the Curie temperature; for antiferromagnetic materials, this temperature is called the Neil temperature.

Some people think that the attraction between magnets and ferromagnetic materials is the earliest human understanding of magnetism.