A realistic model of spin-transport in dilute He-3 in He-4 in a finite geometry

摘要

We have investigated the spin-motion of spin-polarised solutions of Fermi-liquid He-3 in He-4 below 100 mK. The linearised version of the equation of motion is solved for a finite cylindrical geometry with fully spin-reflecting boundary conditions, and is used to model an actual NMR spin-echo experiment. We include non-linear gradients as well as the applied, linear gradient and we have also incorporated the effect of finite-amplitude NMR excitation pulses. We find that the presence of boundaries causes marked deviation from the analytical expressions previously used for data analysis. The non-uniform gradient causes spin-echoes to be delayed and it is noted that the finite amplitude pulses also have a significant effect on the appearance and timing of spin-echoes. Previous values for the 'anisotropy temperature' in the spin-polarised Fermi-liquid, derived experimentally from spin-echoes, are shown to be overestimates. (C) 2003 Elsevier Science B.V. All rights reserved. [References: 12]