The Spin Wave Theory in Antiferromagnetic Heisenberg Model on Face Centered Cubic Lattice

The classical ground states of face centered cubic lattice with nearest neighbor antiferromagnetic Heisenberg interactions are shown to have continuous degeneracy. The spin wave theory removes the degeneracy and determines the ground state, in which the energy E g and spin reduction are calculated. E g is also obtained by calculating the lowest energy of finite size systems and extrapolating to infinite lattice. Both results are in fairly good agreement with each other. Finally it is concluded that the sublattice long range order exists.