NMR ON SUPERFLUID HE-3 IN AEROGEL

The transition to superfluidity of He-3 in high porosity (98.2%) aerog el has been observed by nuclear magnetic resonance techniques. The ons et of the transition at all pressures above 13 bar is marked by a shar p increase in NMR frequency similar to that observed in bulk He-3-A. T his suggests that tile aerogel/superfluid phase is highly homogeneous although both tile transition temperature, T-c, and the amplitude of t he order parameter are substantially suppressed. The aerogel strands a re similar to 50 Angstrom in diameter, much smaller than the superflui d coherence length. Consequently, we have attempted to interpret our o bservations as an impurity scattering problem. Based on our measuremen ts of the magnetic field dependence of T-c it appears that both magnet ic and potential scattering play important roles where the magnetic sc attering can be associated with solid He-3 oil tile aerogel surface. T his is determined by isotopic exchange with He-4, a process which appe ars to stabilize a new superfluid state similar to the bulk B-phase.