Ferromagnetism of He-3 films in very low applied fields

He-3 films on graphite provide a model system for 2D magnetism. At low temp eratures es, the thermodynamic properties of these films are dominated by e xchange interactions. However more subtle interactions such as dipolar coup ling and other anisotropies may eventually play a substantial rolen especia lly in small magnetic fields. Our recent experiments use a SQUID system for both pulsed and continuous wave NMR at very low applied fields (B < 1mT). The spin polarization can be estimated from both the amplitude and frequenc y shift. We find that at coverages above 20 atoms/nm(2) there is a field in dependent (zero field) magnetization at finite temperatures. The temperatur e where this magnetization develops is significantly below J/k where J is t he effective exchange energy. Although the apparent ordering occurs over a broad temperature range, there is a trend towards a "narrowing" of the tran sition region down to the lowest applied fields. Contrary to recent estimat es of exchange parameters which assume a single phase, we find that below 2 4 atoms/nm(2), only a fraction of the spines contribute to the ferromagneti c behavior. This is more consistent with a mixed phase system in that cover age region.