Measurement of the Pauli susceptibility of lithium and sodium by spin-resonance transmission

Abstract

The intensity of the conduction-electron spin-resonance transmission signal in the regime of completely damped spin waves has been measured as a function of specimen thickness in lithium at 300 K and in sodium at 77 K. Theoretical expressions for on-resonance intensity as a function of specimen thickness are characterized by a decay length ${\ensuremath{\delta}}_{s}^{*}={(2{D}^{*}{T}_{2}^{*})}^{\frac{1}{2}}$, where ${D}^{*}$ is the magnetization diffusion coefficient and ${T}_{2}^{*}$ is the transverse relaxation time. A fit of these expressions to the data gives values of ${\ensuremath{\delta}}_{s}^{*}=23\ifmmode\pm\else\textpm\fi{}2$ \ensuremath{\mu}m for lithium and 44\ifmmode\pm\else\textpm\fi{}5 \ensuremath{\mu}m for sodium at these temperatures. Measured values of ${T}_{2}^{*}$ were (1.7\ifmmode\pm\else\textpm\fi{}0.2) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}7}$ sec for lithium and (3.7\ifmmode\pm\else\textpm\fi{}0.5) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}8}$ sec for sodium. Analysis of these measurements in terms of the Landau theory of Fermi liquids leads to a determination of the many-body enhanced susceptibility $\frac{\ensuremath{\chi}}{{\ensuremath{\chi}}^{0}}$, whose values are 2.86\ifmmode\pm\else\textpm\fi{}0.7 for lithium and 2.45\ifmmode\pm\else\textpm\fi{}0.7 for sodium. The result for lithium is in good agreement with other measurements, but the value for sodium is not. Surface relaxation effects appear to be important in sodium, and their contribution is discussed.