A permanent magnet, as its name implies, is an object that can retain its magnetism for a long time without an external magnetic field. According to the material, it can be kept for 10 years. Permanent magnets can be made of ferromagnetic materials such as iron or nickel.
Its atomic structure is special, and the atom itself has magnetic moments. Generally these mineral molecules arranged disorder, influence each other just don't show the magnetic magnetic area. But when the external forces are aligned in the direction of the magnetic field, they show magnetism, which is known as the magnet. Iron, cobalt and nickel are the most commonly used magnetic materials.
Basically magnets are divided into permanent magnets and soft magnets. A permanent magnet is a combination of strong magnetism that makes the spin of the magnetic material in a fixed direction with the angular momentum of the electron. A magnet is just a general term, a general term that is magnetic, and the actual composition does not necessarily contain iron.
A pure metal state itself has no permanent magnetic iron, only close to the permanent magnets can produce magnetic induction, general permanent magnet inside added other impurity elements such as carbon to make magnetic stabilized. Iron is a common magnetic element, but many other elements have stronger magnetic properties, such as strong magnets, such as neodymium, iron, and boron.
After the magnetization of the material, under the influence of the external energy, such as heating, impact, the various magnetic from the direction of the magnetic domain becomes inconsistent, magnetic will weaken or disappear, this process is called demagnetization. Another common method is to place magnetic material in an alternating magnetic field, weakening the strength of the alternating magnetic field until it disappears, and the material is demagnetized.