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 x3 was adjusted close to the value xc≈3.8% at which the spin-rotation parameter μM0 vanishes. In this way the transverse and longitudinal spin-diffusion coefficients D⊥,D∥ were measured while keeping |μM0|<1. It is found that the temperature dependence of D⊥ deviates strongly from 1/T2, with anisotropy temperature Ta=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.
PHYSICAL REVIEW LETTERS