We have estimated the effect on the long-wavelength spin-wave spectrum of the large spin fluctuations in a nearly ferromagnetic Fermi liquid, in order to investigate the possibility of observing spin waves in liquid ${\mathrm{He}}^3$. The study is based on a general formula, which we derive from the spin conservation law, for the long-wavelength spin-wave dispersion curve and the paramagnon model. With the parameters of the model fixed by the ${\mathrm{He}}^3$ susceptibility and the spin-diffusion coefficient data, the width of the spin-wave line and its shift from the Larmor frequency are estimated as functions of the temperature, the pressure, and the wavelength of the spin wave. The spin diffusion coefficient is obtained from the large damping limit of the dispersion formula.

• Received 11 March 1968

DOI:https://doi.org/10.1103/PhysRev.174.227