How Does Magnetic Hysteresis Affect Permanent Magnets?

Magnetic hysteresis refers to the lag between magnetization and demagnetization when a magnetic material is exposed to a changing magnetic field. It affects how well a permanent magnet retains its strength. When magnetized, the magnetic domains inside a material align in one direction. Even after the external field is removed, some alignment remains—this is remanence or residual magnetism. 

However, reversing or weakening the external field can gradually cause domain misalignment, reducing magnet strength. The degree of resistance to this reversal is called coercivity. Materials with high coercivity, like hard steel or alnico, make good permanent magnets because they resist demagnetization. In contrast, soft magnetic materials (like pure iron) have small hysteresis loops, meaning they magnetize and demagnetize easily—useful in transformers. The hysteresis loop graph shows this relationship between magnetic field strength and magnetization. 

A wider loop means stronger retention but more energy loss during cycles. For permanent magnets, controlling hysteresis ensures long-lasting performance. Engineers use materials with large hysteresis loops for strong magnets and small loops for fast-switching devices. Understanding hysteresis helps design efficient electrical machines, memory devices, and magnetic sensors.