Depth Dependence Of Iron Diffusion In Fe3si Studied With Nuclear Resonant Scattering

The access to x-rays of third generation synchrotron radiation sources enables studies of dynamics in metallic systems. The nuclear resonant scattering (NRS) method provides information about elementary atomic jumps. When used in grazing incidence geometry, the sensitivity of the NRS method can be tuned to the surface region. This makes the method especially useful for thin film investigations. Contrary to other surface sensitive methods this technique is not only limited to the surface itself: it allows to retrieve the depth profile of diffusivity from the surface down to the bulk region of the measured sample. Fe-Si intermetallic films with a D0(3) structure and close to the stoichiometric Fe3Si composition have been prepared on an MgO (100) substrate. The NRS measurements in grazing incidence geometry yielded maximum iron diffusivity at the surface and diminishing continuously with the depth. The depth and temperature dependence have been measured and compared with the bulk values.