Diffusion of iron in copper studied by Mössbauer spectroscopy on single crystals

The broadening of the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ Mössbauer line due to diffusion jumps of iron atoms in a copper single crystal has been measured as a function of crystal orientation and temperature between 1060 and 1313 K. The results are the following: (i) The anisotropy of the broadening agrees with what is expected for 〈110〉 jumps into nearest-neighbor vacancies. (ii) The deviation of the measured anisotropy from the curve predicted for self-diffusion permits the determination of the vacancy jump frequencies in the neighborhood of the iron impurity. The best fit indicates that association and dissociation jumps of the vacancy with or from the impurity are slower, but internal jumps in the vacancy-impurity complex are faster than vacancy jumps in the unperturbed copper lattice. (iii) From the temperature dependence of the resonant intensity (the area of the Mössbauer line) it can be concluded that there is no significant impurity-vacancy binding. (iv) The diffusion coefficient for iron in copper and its temperature dependence are in good agreement with tracer results. At 1313 K, D=(4.2±0.3)×${10}^{\mathrm{-}13}$ ${\mathrm{m}}^2$/s.