Experimental determination of the Landau Fermi-liquid-theory parameters: Spin waves in rabidium

This paper presents the results of a study made on spin waves in high-purity rubidium foils at cryogenic temperatures (≈ 1.4 K). The measurements were made using the microwave-transmission technique at $X$-band microwave frequencies and represent an extension of previous measurements in sodium and potassium. From a comparison of the data with theoretical line-shape formulas based on the Landau Fermi-liquid theory, we deduce values of the first three Legendre coefficients of the spin-dependent part of the Landau interaction function. The values are $B_0=-0.21\mathrm{}\pm 0.05$, $B_1=+0.03\mathrm{}\pm 0.08$, and $B_2=-0.09\mathrm{}\pm 0.1$. The errors are not independent, and the consequent relationships between the coefficients consistent with our measurements are presented in detail. A discussion of the particular experimental difficulties encountered and their implications for the analysis is given. We include an analysis of a simple model that exhibits the essential features of spin-wave behavior in itinerant interacting electron systems.