Question

why is diamagnetic in contrast almost independent of temperature?

Answer 1

In a sample of diamagnetic substance, each molecule is not a magnetic dipole itself. So, the random thermal motion of the molecules does not affect the magnetism of the sample. Thus, thediamagnetism is almost independent of temperature

Answer 2

HEY DEAR ...

This is largely temperature independent because there is a large energy (temperature) barrier between the ground state (used to calculate diamagnetic susceptibility) and excited states (at least those which would contribute to the diamagnetic susceptibility).

HOPE , IT HELPS ...