LONGITUDINAL AND TRANSVERSE SPIN-DIFFUSION IN HE-3-HE-4 SOLUTIONS IN A STRONG MAGNETIC-FIELD

Using pulsed NMR techniques, we have measured spin diffusion in He-3-H e-3 solutions with He-3 concentrations of 0.05%, 0.1%, 0.46%, 1.0%, 3. 8% and 6.4% in a magnetic field of 8.8 Tesla for a temperature range 1 1 mK less than or equal to T less than or equal to 200 mK. We observe that the temperature dependence of the transverse spin diffusion coeff icient D-perpendicular to deviates from that expected for an unpolariz ed Fermi liquid in the degenerate region in the 1.0%, 3.8% and 6.4% so lutions. Moreover, by measuring both longitudinal and transverse spin diffusion coefficients in the 6.4%-mixture, we have verified experimen tally the difference between them, and provided direct evidence for a field-induced anisotropy in spin diffusion. The results from the 0.05% and 0.1% solutions show agreement with the theory of Jeon and Mullin; however, no deviation of D-perpendicular to from that expected in an unpolarized mixture was observed because the He-3 is not in the degene rate regime for these very dilute systems for the temperatures we coul d achieve. The analysis of our measurements in terms of the Leggett-Ri ce equations also yields values for the spin rotation parameter mu M(0 ). Using our results along with previous measurements at various He-3 concentrations, we deduce a value for the s-wave quasiparticle scatter ing length of a = -0.88 +/- 0.05 Angstrom.