A-B transition of superfluid 3He in aerogel and the effect of anisotropic scattering -: art. no. 094519

We report the results of high-frequency acoustic shear impedance measurements on superfluid He-3 confined in 98% porosity silica aerogel. Using 8.69 MHz continuous wave excitation, we measured the acoustic shear impedance as a function of temperature for the sample pressures of 28.4 and 33.5 bar. We observed the A-B transition on warming in zero magnetic field. Our observations show that the A and B phases in aerogel coexist in a temperature range of about 100 mu K in width. We propose that differences in the relative stability of the A and B phases arising from anisotropic scattering can account for our observations.