How does a magnetizing field align magnetic domains?

In ferromagnetic materials, such as iron, nickel, and cobalt, the material is composed of small regions called domains, each of which is magnetized to saturation. In an unmagnetized state, these domains are oriented randomly, resulting in no net magnetic field.123

When a magnetizing field is applied, the domains align through a three-stage process:1

• Low magnetizing field: Domains already oriented in the general direction of the field grow at the expense of those unfavorably oriented through the reversible movement of domain walls.1
• Medium magnetizing field: Larger, often irreversible movements of domain walls occur, significantly increasing the volume of favorably oriented domains.1
• High magnetizing field: Remaining domain walls are swept out of the specimen, and the magnetization directions of the domains rotate until they are parallel to the applied field, reaching saturation.1

While some alignment is temporary, permanent magnetization occurs when these domains remain aligned after the external field is removed, a process influenced by the material's internal structure and obstacles to domain wall movement.12