Why can some materials be turned into magnets? It’s all thanks to magnetic domains
In ferromagnetic materials, like iron and nickel, groups of atoms band together in areas called domains. The magnetic strength and orientation, also called the magnetic moments, of the individual atoms in such a domain are aligned with one another and all point in the same direction. It’s those special domains that can turn the material into a magnet.
Every electron is a teeny tiny magnet. They have a north and a south pole and spin around an axis. This spinning results in a very small but extremely significant magnetic field.
In most materials, the magnetic orientation of one electron cancels out the orientation of another. When a material is ferromagnetic, though, those electrons and their magnetic fields join together and their axes align. This makes those little magnetic fields add up, instead of cancelling out.
The tutorial below shows you how these domains respond to an outside magnetic field.
Observe the different directions the arrows inside the piece of ferromagnetic material are pointing. Each arrow represents the magnetic orientation of a domain.
Move the bar magnet closer to the ferromagnetic material by using the slider.
Watch how the magnetic orientation of the domains rotate along an axis when they’re effected by the magnetic field of the bar magnet.
Once the magnetic fields are all aligned, hit reset.
See what happens to the domains when you have the magnet in different positions. Reset to try again.
When all the domains inside of the ferromagnetic material are aligned you have created a new permanent magnet. When magnetized, the magnetic moments of the atoms inside of the ferromagnetic material are organized to create a macroscopic magnet, meaning the piece of material has a north and south pole.
There are only four elements in the world that are ferromagnetic at room temperature and can become permanently magnetized: iron, nickel, cobalt and gadolinium. Ferromagnets stay magnetized for a long time, sometimes for millions of years. Magnet magnetic domains
Magnetic domains refer to regions within a magnetic material where the atomic magnetic moments are aligned in the same direction. These domains play a crucial role in determining the overall magnetic properties of a material.
In a non-magnetized material, the magnetic moments of individual atoms or ions are randomly oriented, resulting in no net magnetic field. However, when an external magnetic field is applied to the material, the magnetic moments tend to align with the field direction. As the field strength increases, more and more magnetic moments align, leading to the formation of magnetic domains. Magnet magnetic domains
Each domain acts as a tiny magnet with its own north and south poles. Within a domain, the magnetic moments are aligned parallel to each other, while neighboring domains may have different orientations. The boundaries between these domains are known as domain walls.
The size and shape of magnetic domains depend on various factors such as temperature, crystal structure, and the presence of impurities or defects in the material. At low temperatures, domains tend to be larger and better defined. As temperature increases, thermal energy disrupts the alignment of magnetic moments, causing domains to shrink and become less distinct. Magnet magnetic domains
The behavior of magnetic domains can be understood using the concept of exchange interaction. This interaction arises from the quantum mechanical exchange coupling between neighboring atoms or ions in a material. It tends to favor parallel alignment of adjacent spins, leading to the formation of well-defined domains.