Transmission Electron Spin Resonance in Dilute Copper-Chromium Alloys

Abstract

Utilizing the transmission conduction-electron spin-resonance technique, we have observed the spin resonance associated with the combined local-moment-conduction-electron system in Cu-Cr over the temperature range 1.4-40\ifmmode^\circ\else\textdegree\fi{}K and concentration range 4-36 ppm. The measured $g$ values, linewidths, and lineshape parameters are interpreted utilizing the Hasegawa model extended to include electron magnetization diffusion and additional local-moment relaxation modes. The predictions of this phenomenological model successfully account for the behavior of the system and we are able to deduce the following parameters: the intrinsic $g$ value for Cr in Cu (2.006\ifmmode\pm\else\textpm\fi{}0.002), the spin-flip scattering rate of the conduction electrons in copper by the Cr impurities ($\frac{1}{{T}_{\mathrm{sl}}}=4.8\ifmmode\times\else\texttimes\fi{}{10}^{+7}$ ${\mathrm{sec}}^{\ensuremath{-}1}$/ppm), the intrinsic (phenomenological) relaxation rate of the Cr to the copper lattice ($\frac{1}{{T}_{\mathrm{dl}}}=2.1\ifmmode\times\else\texttimes\fi{}{10}^{9}$ ${\mathrm{sec}}^{\ensuremath{-}1}$), a lower limit to the effective $s\ensuremath{-}d$ exchange coupling ($|J|\ensuremath{\ge}0.3$ eV), and the ratio of the local moment to conduction-electron spin susceptibilities. Combining this ratio with a separate measurement of the local-moment susceptibility, we are able to determine the conduction-electron spin susceptibility of pure copper. This value, (1.08\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ emu/g, is compared with the free-electron theory from which ${F}_{0}$, the first spin-dependent parameter of the Landau-Fermi liquid theory, is deduced.