What are magnetic domains?

Magnetic domains, also called magnetic regions or magnetic zones, are region-like areas in a ferromagnetic material where the magnetic moments of the atoms or molecules are aligned in a particular direction. Each domain represents an independent microscopic magnetic unit.

How are magnetic domains formed?

In a non-magnetised ferromagnetic material, the magnetic moments of the atoms or molecules are randomly arranged, resulting in an overall magnetic field of zero. However, as soon as an external magnetic field is applied, domains can form. Within each domain, the magnetic moments exhibit strong parallelism.

The size and number of magnetic domains depends on various factors, including, for example, material composition, structure and temperature. Some materials may have a large number of small domains, while other materials may have larger domains. The domains can have different shapes, including round, elongated or other complex shapes.

The boundaries between magnetic domains are called domain walls. Domain walls are transitional regions where the magnetic moments gradually change from one domain to the next.

The formation of magnetic domains exerts a great influence on the magnetic behavior of materials. If an external magnetic field is applied, this influences the orientation of the magnetic moments within the domains. The domains with magnetic moments pointing in the same direction as the external field are favored and grow at the expense of domains with opposite orientation.

The process by which domains form and arrange is called magnetization. Magnetization allows ferromagnetic materials to retain a residual magnetic magnetisation even after the external magnetic field has been removed. This effect is called remanence and is responsible for the magnetic property of permanent magnets.

Where are magnetic domains used?

The control and manipulation of magnetic domains is of great importance in magnetic data storage, such as hard drives. By selectively moving domain walls, information can be stored and retrieved. Furthermore, magnetic domains and domain walls are used in magnetic resonance imaging (MRI).