Most people have played with magnets in childhood and know that magnets can attract iron nails and repel other magnets. However, few people truly understand the underlying principles and classifications of magnets. Essentially, a magnet is a material with neatly arranged internal magnetic domains that can generate an external magnetic field. It only attracts ferromagnetic substances such as iron, cobalt, and nickel, and produces no magnetic attraction for copper, aluminum, plastic, glass and other common materials.
All magnets have two poles: the North (N) pole and the South (S) pole, following the fixed physical law that like poles repel and opposite poles attract. No matter how many pieces a magnet is cut into, each fragment will form a complete set of magnetic poles independently, and there are no independent single-pole magnets in nature. When a magnet is exposed to high temperatures, strong physical impact or intense current shock for a long time, its internal magnetic domain arrangement will become disordered. This will cause gradual demagnetization and a significant reduction in magnetic force.
Commercially available magnets are mainly divided into two categories: permanent magnets and electromagnets. Permanent magnets can maintain stable magnetism for a long time without power supply. Common types include cost-effective ferrite magnets, high-magnetism NdFeB magnets, and AlNiCo magnets, which are widely used in civilian products and small-sized equipment. Electromagnets rely on energized coils to generate magnetic fields; their magnetism disappears immediately after power off, and the magnetic force can be adjusted by changing the current intensity, making them ideal for large-scale industrial control scenarios.
Magnets have been applied since ancient times. Ancient humans made compasses from natural lodestones to solve the direction-finding problems of long-distance travel and maritime navigation. In modern life, magnetic accessories for refrigerators, speakers, mobile phones and doors and windows can be seen everywhere. In the industrial field, magnets are essential for motors, generators, magnetic fixtures and lifting suction cups. High-end industries including new energy vehicles, wind power generation, medical MRI equipment and precision instruments are highly dependent on high-performance NdFeB permanent magnetic materials. Tiny magnetic materials have become indispensable basic industrial raw materials that support the operation of modern society.