DOMAIN-WALLS DUE TO ANISOTROPIC DIFFUSION IN 3.8-PERCENT HE-3-HE-4 SOLUTIONS

Nonlinear anisotropic spin diffusion is considered in He-3-He-4 soluti ons at the He-3 concentration 3.8% where spin-rotation effects are abs ent. For large anisotropy D-parallel to much greater than D-perpendicu lar to it is shown that a long-lived domain wall solution exists in wh ich transverse magnetization is confined in a tube between two reservo irs of up and down spins, as in a longitudinal spin diffusion experime nt. This is possible when D-parallel to much less than D-perpendicular to because diffusion of the transverse magnetization away from the do main wall is balanced by longitudinal diffusion toward the wall. Furth ermore, the spin current between the up- and down-spin reservoirs is r educed because the spins must diffuse through the domain wall via tran sverse diffusion. The decay rate of the wall due to small external and demagnetizing field gradients is also calculated.