  Inelastic neutron scattering measurements on the low energy spin waves in
CaFe2As2 show that the magnetic exchange interactions in the Fe layers are
exceptionally large and similar to the cuprates. However, the exchange between
layers is ~10% of the coupling in the layers and the magnetism is more
appropriately categorized as anisotropic three-dimensional, in contrast to the
two-dimensional cuprates. Band structure calculations of the spin dynamics and
magnetic exchange interactions are in good agreement with the experimental
data.
