CEMS Investigations of Swift Heavy Ion Irradiation Effects in Tb/Fe Multilayers

Abstract : In nanometric Tb/Fe multilayers, the effect of the electronic energy loss of fast heavy ions on the interfaces has been selectively investigated by 57Fe conversion electron Mössbauer spectrometry, thanks to deposition of 57Fe 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 57Fe 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 ∼60 keV/nm), severe mixing leads to the interdiffusion of the layers.