Determination of Anisotropic Relaxation Times in Copper by Cyclotron Resonance

A theoretical and experimental technique has been developed for the study of conduction-electron relaxation times in metals through the use of cyclotron resonance spectra in single crystals. The relaxation times of electrons in two orbits in a magnetic field in copper have been compared in two specimens of differing purity. One orbit is the [111] "belly" ($B$); the other orbit is one which was first seen in this study and is attributed to the "six-cornered rosette" ($R$). Computer programs have been written to curve-fit data to the nonlinear functions describing the experimental spectra which contain effective masses in the ratio $\frac{{m_R}^{*}}{{m_B}^{*}}=1.12\mathrm{}$. The experimental results give $\frac{{\tau }_B}{{\tau }_R}=1.6\mathrm{}\pm 0.5$ for the ratio of the impurity relaxation times when each sample has the same scattering anisotropy.