Ferromagnetic materials are best for magnetization. They contain small regions called domains that each behave like small magnets. When placed in an external magnetic field, the domains align parallel to the field, making the entire material magnetized. Even after removing the external field, ferromagnetic materials retain some magnetization due to hysteresis, requiring a reverse field to fully demagnetize them. Hard magnetic materials have high retentivity and coercivity, giving a rectangular hysteresis loop, while soft materials have low remanence and a narrow loop. Ferromagnetic materials find applications in data storage, information processing, generators, and more.