Effects of a dipolar field in the spin dynamics of a Fermi liquid

We study the spin dynamics of a normal Fermi liquid taking into account the demagnetizing field produced by the spin system itself. Linear solutions of the spin dynamics equations in the form of standing spin waves in a finite volume of liquid are found. At almost all known experimental conditions the influence of demagnetizing field can be satisfactorily described by the first order of perturbation theory. We carried out perturbational calculations for two geometries of experimental cell—spherical and finite cylindrical. We performed also exact numerical simulations of the spin-wave spectra in a spherical cell at an arbitrary strength of the demagnetizing field. The obtained results are applied in particular to conditions of recent experiment [G. Vermeulen and A. Roni, Phys. Rev. Lett. 86, 248 (2001)] related to the problem of zero-temperature transverse relaxation in a polarized Fermi liquid. We found that not taking into account the demagnetizing field leads to negligible errors in the measured relaxation time, thus supporting the conclusion of the absence of zero-temperature spin-wave damping.