NMR EXPERIMENTS ON PURE HE-3 AND HE-3-HE-4 MIXTURES IN SILICA AEROGEL

We have carried out a series of NMR experiments on He-3 systems Filing the pores of silica aerogel with 95% porosity. The systems studied included He-3-He-4 mixtures with a wide range of He-3 concentrations x(3) as well as pure He-3. All experiments were conducted in an 8 T field and for temperatures T greater than or equal to 6 mK. This resulted in strong spin polarization at the lowest temperatures (zip to approximately 80%) for the localized layer observed for a pure He-3 sample. Far pure He-3, the magnetic behavior is dominated by the localized spins, which are found to constitute 6% of the sample. The coupled system of localized plus liquid spins displays rapid transverse magnetization relaxation with an anomalous temperature dependence. For intermediate x(3) magnetization measurements provide a preliminary indication of the phase diagram of mixtures Filing this porous material. The magnetization is hysteretic over some ranges Of x(3).