Anomalous copper diffusion through samarium

We report the observation of enhanced diffusion of Cu through thick films of Sm at temperatures of 250–300 K. The rate of diffusion of Cu to the surface is found to be independent of temperature. The time dependence of the intensities of the Sm divalent and trivalent features indicate the Cu occupies interstitial sites below the divalent Sm surface layer and above the trivalent Sm bulk. The measured binding energies of the divalent and trivalent Sm show no shift with respect to pure Sm, indicating the Cu does not react with the Sm. The spectral features associated with Cu indicate it is in an atomic-like configuration. An examination of these intensities also provide evidence for heterogeneous mixed valence in Sm.