Magnetic Materials

Many materials, including some metals and ceramics, are magnetic. The most common type of magnetic materials we use are ferromagnets. Ferromagnets have a strong magnetic field with north and south poles. A compass needle is an example of a ferromagnet.

 
magnet
A bar magnet

Magnetic materials get their properties from the electrons of the atoms in the materials. The electrons in each atom, as governed by the rules of quantum mechanics, interact to give rise to a magnetic moment for each atom. Depending on the way these magnetic moments interact with each other, a material can exhibit one of the four different types of magnetism.

Magnetic materials contain magnetic domains each of which has a particular magnetic moment orientation.

In each domain, the atoms point their magnets in one particular direction. If the domains are randomly oriented, the solid will not have a macroscopic magnetization.

The domains can be forced to align themselves in a particular direction by heating the magnet and cooling it in a magnetic field. The heat supplies energy so that the domains can move in the magnetic field.

 
magnetic domains
Magnetic domains

How are magnets used?

Magnetic materials are used in electrical power applications such as transformers and motors, in video monitor picture tubes to move electron beams, and in computer disks or video or audio tapes to record information.

 

 

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