Collisionless spin waves in normal and superfluid3He

Abstract

Standing spin-wave modes in liquid /sup 3/He have been studied by c-italicw-italic AiNM-italicR-italic at Larmor frequencies of 1,2, and 4 M-italicH-italicz and pressures of 0, 6.3, and 12.3 bar. The spin waves, which produce peaks in the N-italicM-italicR-italic line, are visible at temperatures below 5 m-italicK-italic at zero pressure. With the assumption of a slightly simplified sample shape and no transverse spin relaxation at the walls, the theory of Leggett fits the spin-wave frequencies in the normal liquid very well, giving a value of the Fermi liquid parameter F/sub 1//sup a/ = -0.6 +- 0.2 at zero pressure. The width of some of the peaks is larger than expected from other determinations of the quasiparticle diffusion time tau/sub D/. This could be due to wall relaxation or to deviations from the assumed sample geometry. In the superfluid A-italic/sub 1/ and A-italic phases, where the data cannot be fitted to existing theories, the spin-wave modes are shifted in frequency and suffer additional damping as the temperature is decreased. At still lower temperatures in the B phase an inversion of the spin-wave modes are shifted in frequency and suffer additional damping as the temperature is decreased. At still lower temperatures in themore » B-italic phase an inversion of the spin-wave spectrum from one side of the N-italicM-italicR-italic line to the other is observed, agreeing quantitatively with the predictions of the 1975 theory of Combescot.« less