What is the physical significance of the Curie constant? I understand it depends on the effective moment of the ion and hence must be some measure of it, but what is it exactly? Like some average moment per magnetic atom or average moment of the solid overall? Or what? If it were to be explained non-mathematically, then how would you define it?
I would say it is a measure of how strongly a material is able to sustain magnetic alignment despite thermal fluctuations.
Which will obviously be determined by how strongly each atoms couples to the magnetic field (magnetic moment and angular momentum) and the density of such atoms.