Growth study of epitaxial FexZn1-xF2 thin films

The FexZn1-xF2 alloy has been shown to be a model system for studying the m agnetic phase diagram of dilute magnets. Whereas the growth of bulk single crystals with fixed Zn concentrations is difficult, the thin film growth is comparatively simpler and more flexible. To gain an understanding of the g rowth of FexZn1-xF2 films, a method was developed to grow smooth films at f ixed concentrations. This was done by depositing a MgF2 buffer layer on MgF 2(001) substrates and then depositing FeF2 and ZnF2 [001]-orientated epitax ial thin films at different temperatures. Surprisingly, the lattice spacing depends strongly on the growth temperature, for 44-nm-thick FeF2 films and 77-nm-thick ZnF2 films. This indicates a significant amount of stress, des pite the close lattice match between the films and the MgF2 substrate. Thic k alloy samples (approximately 500 nm thick) were grown by co-evaporation f rom the FeF2 and ZnF2 sources at the ideal temperature determined from the growth study, and their concentration was accurately determined using x-ray diffraction.