Diamagnetics are temporary weak magnets posses magnetism only when placed in external magnetising field. It is found in the atoms or molecules having even number of electrons. In the unmagnetized form of a diamagnetic the magnetic moments of the two electrons having same value of principle quantum number ‘n’ have equal & opposite value cancel out, thus producing net zero magnetic moment. However when placed in an external magnetic field the electron having dipole moment opposite to external magnetic field is accelerated & other one retards, producing a net non zero magnetic moment in a direction opposite to the applied magnetic field. Diamagneitcs get repelled weakly by magnetizing fields. Now when external magnetic field is switched off, the magnetic force on electrons again becomes zero, due to which the two magnetic moments again become equal & cancel each other.