The third graph is the structure of the lattice we are inter

The third graph is the structure of the lattice we are interested in, and there are 2 graphs shows energy and entropy, we can see there is residual entropy in our graph.

Why it is happen and how does this related to the spin structure? (plz include the spin stucture graph)

Thanks!

Solution

Residual entropy to the inherent latent heat which would be released upon cooling if the reversible path were available. The nature of this heat is that if the crystal possessing residual entropy freezes above its Boltzmann’s
characteristic temperature of molecular alignment, the difference in energy between different molecular arrangements is overcome by the kT heat bath to form a nearly-ideal solution. However, upon cooling below this characteristic temperature, they would separate with a concomitant release of the corresponding energy, provided the reversible path were available.

For spin structure part read this paper (I don\'t have axcess to this!)

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.134434