The susceptibility of diamagnetic - substances is negative.
Diamagnetic substances are feebly magnetized in a direction opposite to that of the field. Thus, the susceptibility of diamagnetic substances is negative. Further the flux density in a diamagnetic substance placed in a magnetizing field is slightly less than that in the free space. The relative permeability of diamagnetic substances is less than 1. Hence, these substances are feeble repelled by a magnet while paramagnetic substances are feebly attracted by a magnet and ferromagnetic substances are strongly attracted by a magnet.