Magnetism of matter
Materials can be divided into three types: ferromagnetic, paramagnetic, and diamagnetic, depending on how they react to an external magnetic field.
Ferromagnetic
In ferromagnetic materials, each atom acts like a magnet. In ferromagnetic materials, the atomic magnets are aligned in the same direction as the external magnetic field when an external magnetic field is applied. Magnetized ferromagnetic materials can attract other ferromagnetic materials like a magnet.
(Example) Iron, nickel, cobalt
Ferromagnetic materials maintain magnetization for a long, even when an external magnetic field is removed. This phenomenon is used in credit cards, recording tapes, computer storage devices, etc. However, strong magnetic fields, high temperatures, or large impacts can erase magnetized ferromagnetic materials.
Paramagnetic
The atomic magnets inside the Paramagnetic material are weakly magnetized toward the external magnetic field and weakly attract the magnet. When the external magnetic field is removed, the magnetic effect disappears immediately.
(Example) Paper, aluminum, magnesium, tungsten, platinum, liquid oxygen, etc.
Diamagnetic
When a magnetic field is applied from the outside, the atomic magnets inside the material are magnetized in the opposite direction to the external magnetic field and do not stick to the magnet. In the case of diamagnetic metals, a counter-electromotive force is generated, which becomes the principle of a generator.
(Example) Water, mercury, lead, copper, etc.
Most substances are diamagnetic, but the effect is minimal.
Superconductors have very strong diamagnetism.