An Approximate Quantum Theory of the Antiferromagnetic Ground State
Abstract
A careful treatment of the zeropoint energy of the spinwaves in the KramersHeller semiclassical theory of ferromagnetics leads to surprisingly exact results for the properties of the ground state, as shown by Klein and Smith. An analogous treatment of the antiferromagnetic ground state, whose properties were unknown, is here carried out and justified. The results are expected to be valid to order 1S or better, where S is the spin quantum number of the separate atoms. The energy of the ground state is computed and found to lie within limits found elsewhere on rigorous grounds. For the linear chain, there is no longrange order in the ground state; for the simple cubic and plane square lattices, a finite longrange order in the ground state is found. The fact that this order can be observed experimentally, somewhat puzzling since one knows the ground state to be a singlet, is explained.
 Publication:

Physical Review
 Pub Date:
 June 1952
 DOI:
 10.1103/PhysRev.86.694
 Bibcode:
 1952PhRv...86..694A