What is the role of magnetic domains in magnetism?

Magnetic domains are regions in a magnetic material where the magnetic fields of atoms are grouped together and aligned.

In more detail, magnetic domains play a crucial role in magnetism. They are small, magnetised regions within a magnetic material, where the magnetic fields of individual atoms are aligned in the same direction. This alignment is what gives the material its overall magnetic field.

When a material is not magnetised, the directions of the magnetic fields in its domains are random. This means that the material as a whole does not have a net magnetic field. However, when the material is magnetised, the domains align so that their magnetic fields point in the same direction. This alignment creates a strong magnetic field for the material as a whole.

The size and arrangement of magnetic domains can be influenced by external magnetic fields. When a strong external magnetic field is applied to a magnetic material, it can cause the domains to align even more, increasing the material's magnetic field. Conversely, if the external field is removed, the domains may return to their random orientations, causing the material to lose its magnetism. This is why some materials can be magnetised and demagnetised.

In addition, the boundaries between domains (known as domain walls) can move in response to external magnetic fields. This movement can cause the domains to grow or shrink, changing the overall magnetic field of the material. Understanding how magnetic domains and domain walls behave is important for many applications, including the design of magnetic storage devices.