NMR studies of superfluid 3He in low density silica aerogels

Continuous wave NMR studies of superfluid He-3 in 99.4%, 98.7% and 98.3% porosity silica aerogels show similar phase diagrams, with an equal spin pairing (ESP) A-like state stab le near T-c,T-a, and a B-like phase stable at lower temperatures. On cooling through T-c,T-a, the sample magnetization and frequency shift show substantial supercooling of the A-like phase, with discontinuous changes to B-like behavior seen at about 0.64T(c,b) (bulk) for all samples. On warming, both the frequency shift and magnetization change continuously as the sample enters an ESP state. This suggests that this phase transition is broadened by pinning of the A-B interface on density fluctuations in the aerogel, even very close to T-c,T-a. (C) 2003 Elsevier Science B.V. All rights reserved.