What is Diamagnetism ?

Diamagnetism is the property of an object which causes it to create a magnetic field in opposition of an externally applied magnetic field, thus causing a repulsive effect. It is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field.

Diamagnetic Levitation

Many common materials such as water, wood, plants, animals, diamonds, fingers, etc. are usually considered to be non-magnetic but in fact, they are very weakly diamagnetic. Diamagnets repel, and are repelled by a strong magnetic field. The electrons in a diamagnetic material rearrange their orbits slightly creating small persistent currents which oppose the external magnetic field. Two of the strongest diamagnetic materials are graphite and bismuth.

The forces created by diamagnetism are extremely weak, millions of times smaller than the forces between magnets and such common ferromagnetic materials as iron. However, in certain carefully arranged situations, the influence of diamagnetic materials can produce startling effects such as levitation.

It was proved in 1842 that it is impossible to stably levitate any static array of magnets by any arrangement of fixed magnets and gravity. However, the addition of diamagnetic materials makes such levitation possible. The July 22 Nature paper,Magnetic Levitation at your fingertips,describes two configurations where diamagnetic materials are used to stabilize the levitation of a magnet in the field of a fixed lifting magnet.