| Summary: | We have carried out a series of NMR experiments on $\sp3$He systems filling the pores of silica aerogel with 95% porosity. The systems studied included $\sp3$He-$\sp4$He mixtures in a wide range of concentrations as well as pure $\sp3$He. All experiments were conducted in an 8 Tesla field and for temperatures between 5 and 320 mK. This resulted in strong spin polarization at the lowest temperatures (up to approximately 80%) for the localized layer observed for a pure $\sp3$He sample. For pure $\sp3$He, 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 magnetic relaxation with an anomalous temperature dependence. The longitudinal magnetization is observed to have, at the lowest temperatures, an anomalously long relaxation constant which cannot be readily associated with either the liquid or the localized spins. For mixtures with intermediate concentrations our measurements provide a preliminary indication of the phase diagram of mixtures filling this porous material.
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