Fe-Ag Superlattices by Molecular Beam Epitaxy

We have succeeded in producing high quality (110)Fe/(111)Ag superlattices by Molecular Beam Epitaxy. Important parameters in the production of these materials were substrate temperature and effusion rates of the constituents. We have used SQUID magnetometry, Mössbauer spectroscopy and Reflection High Energy Electron Diffraction to demonstrate flatness and continuity of the films down to a thickness of approximately 2 atomic layers for the iron and 5 atomic layers for the silver. In the case of the thinnest iron layers, no large reduction of the ferromagnetic Curie temperature was observed, although this had been suggested and reported by other investigators. Furthermore, there was no indication for this particular growth system that the magnetization of the iron was out of the plane of the film. Variations of the magnetic hyperfine fields observed in the iron films were seen both as a function of iron thickness and as a function of the thickness of the intervening silver layers. For the thinnest films, the temperature dependence of the magnetization showed a linear behavior rather than the traditional T3/2 form.