The dispersion relation for magnons in a bcc lattice (exchange energy J, expectation value S for spin) is given by:
For the next nearest neighbours in bcc with the coordination number z = 8, this yields in:
This has the same mathematical form as the dispersion relation for electrons in the tight-binding model:
That means the same data as in the tight-binding calculation can be used, only the scale must be changed by replacing some constants:
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The data for the density of states was originally calculated by Thomas Ganner and Klaus Lang here.