Resonant impurity scattering and electron-phonon scattering in the electrical resistivity of Cr thin films

The resistivity as a function of temperature from 0.6 to 300 K for epitaxial and polycrystalline Cr thin films is presented and fit to a model which includes electron-phonon scattering and resonant impurity scattering. Resonant impurity scattering from localized defect states in the spin-density wave gap leads to very high residual resistivity (up to 400 mu Omega cm) and a minimum at low temperatures (below 100 K). This is strong experimental evidence for resonant impurity scattering due to defects in pure Cr rather than dopant atoms. The magnitude of the resistivity minimum scales linearly with the residual resistivity over 2 orders of magnitude. At moderate temperatures (100-300 K) the resistivity shows a positive, linear temperature dependence due to electron-phonon scattering. Defects affect the electron-phonon scattering as well leading to a variation in the effective Debye temperature and resistivity slope between samples, a significant deviation from Matthiessen's rule.