NUCLEAR FERROMAGNETIC AND ANTIFERROMAGNETIC EXCHANGE IN THIN-FILMS OF HE-3 ADSORBED ON GRAPHITE

Measurements of the nuclear magnetic susceptibility of multilayer films of He-3 adsorbed on graphite plated with a monolayer of He-4 are reported for He-3 surface densities up to 0.27 angstrom-2 and temperatures in the range (6 divided-by 600)mK. The coverage dependence of the exchange constant has been measured; this is antiferromagnetic when the second layer first solidifies and becomes ferromagnetic with the formation of a fluid overlayer. The second-layer solid density evolves in a stepwise fashion with increasing coverage, while the susceptibility of the fluid overlayer shows structure associated with layering in the film.