Magnetism is determined by the properties of permanent magnetic materials. If explained in terms of atomic current, the magnetic field generated by the current magnetizes other objects, and the magnetized objects generate electric fields, and the electric fields interact to generate force. Most matter is composed of molecules. Molecules are composed of atoms, and atoms are composed of nuclei and electrons. Inside the atom, the electron rotates continuously and revolves around the nucleus. Both of these movements of electrons produce magnetism. But in most materials, the directions of electrons are different and chaotic, and the magnetic effects cancel each other out. Therefore, most materials do not exhibit magnetism under normal conditions.
Because magnetism is one of the basic properties of matter, all matter is a magnetic medium. There are three types:
1. Paramagnetic substances, this kind of substance produces the same additional magnetic field as the external magnetic field under the action of a magnetic field. Most substances belong to this category.
2. Diamagnetic material, which generates an additional magnetic field opposite to the external magnetic field under the action of a magnetic field, such as copper and inert gas.
3. Ferromagnetic material, this material generates a strong additional magnetic field the same as the external magnetic field under the action of a magnetic field, such as iron, cobalt and nickel.
Ferromagnetic substances such as iron, cobalt, nickel, or ferrite are different. The electron spins in them can spontaneously arrange in a small range to form a spontaneous magnetization zone, which is called a magnetic domain. After the ferromagnetic substance is magnetized, the internal magnetic domains are arranged neatly and in the same direction to strengthen the magnetism and form a permanent magnetic material. The magnetization process of the magnet is the magnetization process of the iron block. The magnetized iron block and the magnet with different polarities generate attraction between the iron block and the magnet firmly, and we say that the magnet is magnetic.