Diamagnets are materials that create a weak magnetic field in opposition to an external magnetic field. This phenomenon occurs because the electrons in diamagnetic materials rearrange themselves slightly when exposed to a magnetic field, resulting in a very weak repulsion. Common examples of diamagnetic materials include bismuth, copper, and graphite. Unlike ferromagnetic materials, which can be strongly attracted to magnets, diamagnets do not retain any magnetization once the external field is removed. This property makes them useful in various applications, such as magnetic levitation experiments and in the design of sensitive measuring instruments.