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°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±0.002), the spin-flip scattering rate of the conduction electrons in copper by the Cr impurities ($\frac{1}{T_{\mathrm{sl}}}=4.8\mathrm{}\times {10}^{+7\mathrm{}}$ ${\sec }^{-1\mathrm{}}$/ppm), the intrinsic (phenomenological) relaxation rate of the Cr to the copper lattice ($\frac{1}{T_{\mathrm{dl}}}=2.1\mathrm{}\times {10}^9$ ${\sec }^{-1\mathrm{}}$), a lower limit to the effective $s-d$ exchange coupling ($\mathrm{}\left|J\right|\mathrm{}\ge 0.3$ 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±0.1)×${10}^{-7\mathrm{}}$ 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.