New Evidence for Zero-Temperature Relaxation in a Spin-Polarized Fermi Liquid

Spin-echo experiments are reported for 3He-4He solutions under extremely high B/T conditions, B=14.75 T and T >= 1.73 mK. The 3He concentration x_3 was adjusted close to the value x_c = 3.8% at which the spin rotation parameter muM_0 vanishes. In this way the transverse and longitudinal spin diffusion coefficients D_perp, D_parallel were measured while keeping |muM_0| < 1. It is found that the temperature dependence of D_perp deviates strongly from 1/T^2, with anisotropy temperature T_a = 4.26 +/- 0.18 mK. This value is close to the theoretical prediction for dilute solutions, and suggests that spin current relaxation remains finite as the temperature tends to zero.