ONSET OF FERROMAGNETIC EXCHANGE IN ADSORBED HE-3 FILMS

Nuclear magnetic resonance experiments are reported on multilayer He-3 films adsorbed on the surface of graphite. Initially the second layer exhibits antiferromagnetic exchange, which has been measured as a fun ction of coverage. Measurements of the nuclear magnetic susceptibility and resonant frequency for coverages around the third layer promotion precisely identify the onset of ferromagnetic exchange in the film. T he evolution of the structure of the film is discussed in the light of these results and previous heat-capacity and NMR data.