Zero-field magnetic order in the boundary layers ofHe3on Grafoil

Abstract

The low-field NMR spectra of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ boundary layers on exfoliated graphite show collective modes for T<1 mK. We measure the amplitude and frequency for these modes with the static $H_0$ field applied parallel to the graphite planes and varying continuously between 0 and 15 G. 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 ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ boundary layers.