Why does the magnet suck iron and what is the principle of the magnet?

Magnetism like magnets is one of the basic properties of matter, and all matter is a magnetic medium. 

Divided into three types: 

1. paramagnetic substances, which produce the same additional magnetic field as the external magnetic field under the action of a magnetic field, and most substances belong to this category,

2. A diamagnetic substance that produces an additional magnetic field opposite to the external magnetic field under the action of a magnetic field, such as copper and inert gases.

3. Ferromagnetic substances, which generate a strong additional magnetic field the same as the external magnetic field under the action of a magnetic field, such as iron, cobalt, nickel, etc.

According to the hypothesis first proposed by Ampere, there is a permanent molecular current with a certain magnetic moment in the paramagnetic molecules.In the absence of an external magnetic field, due to the thermal motion of the molecules, the orientation of these molecular currents is irregular, so the magnetic field they generate is equal to zero on average and does not show magnetism to the outside. When there is an external magnetic field, these molecular currents are oriented by the external field, and their magnetic moment lattice turns to the direction of the external magnetic field, generating an additional magnetic field along the direction of the external magnetic field. That's what magnetizes the paramagnetic. The molecules that make up the diamagnetic mass have an intramolecular structure that makes their molecular current equal to zero in the absence of an external magnetic field. When an external magnetic field is introduced, just as an induced current is generated when a magnetic field is introduced in a closed circular wire, an induced current is also generated in these diamagnetic molecules. Because there is no resistance in the molecule, as in a superconductor, once the current is generated, it will flow forever until the reverse induced current cancels it out when the external magnetic field withers. Under the action of external magnetic field, all magnetic media have to produce induced molecular current, that is, diamagnetism is common to all substances, but in paramagnetic molecules, the magnetic moment of molecular current is much larger than the narrow moment of induced current, so the diamagnetism of substances is covered up and only paramagnetism appears.

And the cause of ferromagnetism, there is a magnetic domain hypothesis:
The magnetic moment of a single atom of many substances is on an order of magnitude, so it is not the magnetic moment of the atom that is affected by the magnetic field that causes the difference between the ferromagnet and other magnetic media. It's because the atoms of a ferromagnet are more likely to line up under an external magnetic field. Why is it so easy to arrange atomic magnetic moments in ferromagnets?? This is because there are molecular fields in ferromagnets due to strong interactions between atoms (called exchange forces). The effect of the molecular field is the same as that of the magnetic field, which makes the atomic moments aligned. The size of the molecular field is much stronger than that of the ordinary magnetic field. For example, at room temperature, more than 95% of the original magnetic moments of iron are aligned due to the effect of the molecular field. However, ferromagnets do not show magnetism before magnetization, because each ferromagnet is actually divided into many small regions, we call these small regions magnetic domains. The molecular field arranges the original magnetic moments of each magnetic domain in the same direction, but the directions of the magnetic moments of each magnetic domain are different from each other. Therefore, in the absence of an external magnetic field, although the original magnetic short in each magnetic domain has been almost completely arranged, the total magnetic short of the iron core is still zero, and the whole ferromagnet does not show magnetism. After adding an external magnetic field, the direction of the magnetic moment of each magnet turns to the direction of the external magnetic field, and the total magnetic moment of the ferromagnet is not zero. In view of the fact that the original magnetic moment in each zi domain is oriented in the absence of an external magnetic field, the iron zi body also shows strong magnetism in a small external magnetic field. When the temperature is higher than a value (Curie point), the magnetic domain collapses and the ferromagnet is lost.Sexquality, the same as ordinary paramagnetic substances.

Source: magnet manufacturers Youlian Magnetic Industrywww.youliancy.com