Evidence for magnetic ordering in the boundary layers of 3He on grafoil

The boundary layer of 3He on exfoliated graphite (grafoil) is an interesting model system for two dimensional magnetism. The low field NMR spectra of 3He boundary layers on exfoliated graphite show collective modes for T<1 mK. We measure the amplitude and frequency for these modes with the static H0 field applied parallel to the graphite planes and varying continuously between 0 and 15 gauss. One of the modes extrapolates to a nonzero frequency and amplitude as the field is dropped to zero. We interpret these nonzero intercepts as an indication of zero field magnetic order in the 3He boundary layers. The possible role of the weak nuclear dipolar interactions will be described.