MAGNETISM IN 2 DIMENSIONS

A brief review is presented of the present state of knowledge (both theoretical and experimental) concerning quasi-two-dimensional Heisenberg ferromagnets and antiferromagnets, and comparisons are made with typical three-dimensional magnetic systems. The greatly enhanced quantum and short-range order effects in two dimensions expose the limitations of most current statistical theories and should stimulate both theoretical and experimental interest in a number of directions. These include zero-point spin deviations (for antiferromagnets), bound-magnon states, possible new phase transitions to disordered states with infinite susceptibility, critical coefficients, the role of anisotropy in stabilizing long-range order in two dimensions, and the study of propagating spinwaves in the paramagnetic phase. © 1969 The American Institute of Physics.