Diamagnetism

In some materials the magnetic moment of all the atomic current loops is zero when no magnetic field is present. These materials still display magnetic effects because an external field alters electron motion within the atoms, causing additional current loops and induced magnetic dipoles. If the additional induced field is in the opposite direction to the external applied field the material is said to be diamagnetic. We may think of the induced field being in the opposite direction to the applied filed as being a consequence of Lenz's Law – the direction of the induced current is such as to oppose the change causing it.

Diamagnetic materials have negative magnetic susceptibilities., and relative permeabilities slightly less than unity. Diamagnetic susceptibilities are very nearly temperature independent.

The magnetic susceptibilities of some diamagnetic materials are shown in the table.