Conduction-electron spin-resonance study of bimetallic samples

The interface between two bulk metals has been studied by observing the conduction-electron spin-resonance (CESR) signal from one of the metals. The interface has been characterized by several parameters—$\lambda$ and $t$, the probabilities that an electron crosses the interface with and without spin relaxation, and $\epsilon$ and $r$, the probabilities that an electron is reflected with and without spin relaxation. Values of these parameters were extracted from the linewidth data by applying a theory which we have developed to calculate CESR line shapes. The systems studied were films of lithium on copper, lithium on manganese, and sodium on aluminum. The copper and manganese substrates were found to produce a temperature-dependent broadening of the normally narrow temperature-independent lithium CESR signal. By comparison, aluminum had little effect on the sodium CESR signal, broadening it slightly. On fitting the data, an upper limit of $t-\lambda <0.005\mathrm{}$ with $t$, $\lambda <0.005\mathrm{}$ was found for all three systems indicating a potential barrier at the interface. Assuming $t=\lambda =0\mathrm{}$ values of $\epsilon \mathrm{}\left(T\right)\mathrm{}$ were extracted from the data. For lithium on copper, $\epsilon$ ranged from $\epsilon \left(250\mathrm{} \mathrm{K}\right)=2\mathrm{}\times {10}^{-3\mathrm{}}$ to $\epsilon \left(80\mathrm{} \mathrm{K}\right)=4.5\mathrm{}\times {10}^{-3\mathrm{}}$; for lithium on manganese ε ranged from $\epsilon \left(250\mathrm{} \mathrm{K}\right)=3\mathrm{}\times {10}^{-3\mathrm{}}$ to $\epsilon \left(80\mathrm{} \mathrm{K}\right)=18\mathrm{}\times {10}^{-3\mathrm{}}$; and for sodium on aluminum $\epsilon \sim 3\times {10}^{-4\mathrm{}}$ independent of temperature. A microscopic explanation of these values is lacking, but the possibility that they are due to intrinsic effects such as dipole fields and magnetic scattering is considered. The possibility that the effects are due to alloying or contamination at the interface is also considered but found unlikely.