It is rigorously proved that at any nonzero temperature, a one- or two-dimensional isotropic spin- Heisenberg model with finite-range exchange interaction can be neither ferromagnetic nor antiferromagnetic. The method of proof is capable of excluding a variety of types of ordering in one and two dimensions.
- Received 17 October 1966
- Published in the issue dated 28 November 1966
© 1966 The American Physical Society