NUCLEAR MAGNETISM OF 2-DIMENSIONAL SOLID HE-3

The properties of two dimensional frustrated magnets have been studied in an investigation of the nuclear magnetism of two dimensional solid He-3. The results of recent heat capacity and NMR measurements on He- 3 films adsorbed on graphite are reported. The coverage dependence rev eals both antiferromagnetic and ferromagnetic regimes and their descri ption in terms of Heisenberg series expansions is discussed. There is clear evidence of frustration by multiple spin exchange, with no magne tic phase transition. 2D He-3 currently provides the best model system for the study of S=1/2 quantum antiferromagnetism on a triangular lat tice. There is evidence that the frustration can be tuned, and hence t he ground state order.