New evidence for zero-temperature relaxation in a spin-polarized Fermi liquid

Spin-echo experiments are reported for He-3-He-4 solutions under extremely high B/T conditions, B = 14.75 T and T greater than or equal to 1.73 mK. The He-3 concentration x(3) was adjusted close to the value x(c) approximate to 3.8% at which the spin-rotation parameter muM(0) vanishes. In this way the transverse and longitudinal spin-diffusion coefficients D-perpendicular to, D-parallel to were measured while keeping \muM(0)\ < 1. It is found that the temperature dependence of D-⊥ deviates strongly from 1/T-2, with anisotropy temperature T-a = 4.26(-0.44)(+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.