SPIN DYNAMICS OF HE-3 IN AEROGEL

We report continuous-wave NMR measurements on superfluid(3) He contain ed inside high porosity aerogel at 3.24 MPa, in a 28.4 mT magnetic fie ld, and down to 0.9 mK. Three different purities of He-3 were used: pu re He-3, He-3 with enough He-4 to replace the first localized layer, a nd He-3 with enough He-4 to replace both localized layers. Below 2.26m K, the NMR spectrum does not consist of a single Lorentzian, but a dis tribution of NMR resonant frequencies both above and below the Larmor frequency, wt. Upon cooling, the component of the spectrum at frequenc ies below the Larmor frequency moves to higher frequencies over a narr ow temperature range and does not return to w < w(L) upon warming. The higher frequency component of the spectrum displays two resolvable pe aks which become a complex structure upon removal of the localized He- 3 spins. The spectrum changes as the magnetic field is rotated about t he axis of the aerogel sample, indicating that the 3He is able to dete ct a preferred direction in the aerogel. The shape of the spectrum sho ws no rotation or magnetic field hysteresis. We find that the average frequency shifts of our NMR spectra do not depend on the presence of t he localized 3He spins. These frequency shifts and the presence of a t emperature-independent magnetization for the liquid 3He suggest that t he aerogel stabilizes a single equal-spin-pairing state in our experim ents.