A LEGGETT-RICE EFFECT IN SOLID HE-3-SPIN ROTATION INDUCED BY EXCHANGE

In solid He-3 the internuclear exchange interaction may be interpreted as a molecular field, as in the Weiss theory of magnetism. In an appl ied magnetic field the magnetic moment precesses about the total magne tic field, to which the molecular field contributes. As Leggett showed for liquid helium in the Fermi liquid region, this leads to a modific ation of the time evolution of the magnetisation; it is no longer pure ly diffusive. In solid He-3 at low polarisation there is conventional spin diffusion; at high polarisations the evolution is in the form of spin waves. We show that the intermediate behaviour may be expressed i n terms of a complex diffusion coefficient of constant magnitude, whos e phase angle depends on the polarisation.