Non-linearity in spin/entropy wave propagation in 3He A1

The spin/entropy wave propagation was observed in a cylindrical resonant cavity filled with superfluid 3He A1 phase in 2 T and 22.9 bar. Oscillating superleak transducers were used with Nuclepore membranes (3 μm pores) as active elements. When the drive is increased to a sufficiently high level, saturation in the resonant response is observed. The observed non-linear response will be interpreted in terms of critical velocity. The effects of superfluid fraction anisotropy on the spin/entropy wave propagation are currently under study by changing the relative orientation between the magnetic field and the sound propagation directions. Results of these studies will be reported