CEMS investigations of swift heavy ion irradiation effects in Tb/Fe multilayers

In nanometric Tb/Fe multilayers, the effect of the electronic energy loss of fast heavy ions on the interfaces has been selectively investigated by Fe-57 conversion electron Mossbauer spectrometry, thanks to deposition of Fe-57 probe layers at the bottom or top of the natural iron layers. The as-deposited Tb-on-Fe interfaces are sharp while the Fe-on-Tb ones are amorphous and diffuse. Modifications of the environments of the Fe-57 probe atoms were investigated as a function of the electronic stopping power (Sn and U ions) and the ion fluence. An effect of recrystallization of iron is evidenced at the initially diffuse Fe-on-Tb interface while only mixing between Fe and Tb atoms is observed at the sharp Tb-on-Fe interface. For very high rates of electronic energy deposition (stopping power similar to60 keV/nm), severe mixing leads to the interdiffusion of the layers.