Diamagnetic materials have their magnetic moment due to spin and there is no net dipole moment due to orbital motion of electrons. In any material having dipole moments due to orbital motion of its electron, many dipoles cling together in same orientation for reasons explained only by invoking quantum mechanics, they are called domains. In the absence of external magnetic field the domains of most materials(except for permanent magnet) are randomly oriented in such a way that net dipole moment at any finite volume is zero, it is only when they are exposed to external magnetic field their diploe try to align in the the direction of external magnetic field but thermal motion try to misalign them so their is a fight between external magnetic field which try to align them and thermal motion due to temperature that wants to misalign them, hence their net magnetic field or permeability is affected by temperature. Such is the case with paramagnetic materials and ferromagnetic materials in both case rise in temperature decreases their net magnetism however the inverse relationship given by curie law is valid for paramagnetic material. Diamagnetic materials got their magnetism not due to orbital motion of electrons but due to spin their magnetic moment being due to spin, so no formation of domains which could be misaligned by thermal motion so their magnetism is independent of temperature. So temperature has no effect the magnetic behaviour of diamagnetic substance.Karthikk Kumaresan said:I know that in a para magnetic material the magnetization increase on cooling. What will be the same effect on a diamagnetic material,considering the fact that Curies law doesn't hold good on diamagnetic materials.