Neutron reflectivity allows to characterise surfaces and interfaces of ultra thin film layered systems down to a nanometric scale (~2 nm). It is especially a powerful tool for the study of magnetic and polymer thin film structures.
The neutron magnetic interaction is very large and makes polarised neutron reflectivity a very sensitive tool for probing magnetic multilayers. It allows the determination of magnetic ordering and coupling in new artificial magnetic multi-layers (either metallic, semi-conducting or oxides). Examples of studies in the field of GMR (Giant Magneto Resistive) sensors used in hard drive and tape read heads will be given. The search for efficient spin-injection materials which could be used in spin electronics is also a growing field of activity. Several material candidates are presently evaluated. Recent studies on such materials will be presented : oxide materials (Fe2O3 - Fe3O4) epitaxial thin films ; multilayer systems involving semiconducting materials ([Fe/Si]n, [GaMnAs/GaAs]).
Besides the high sensitivity of neutrons to magnetism, the possibility of isotopic labelling (H/D substitution) offers a way to probe polymer and protein thin film structures with great details : polymer interdiffusion or polymer grafting can be studied at the substrate/polymer or liquid/polymer interfaces. A model study of PMMA polymer grafting will be presented.