Magnetic Thin Films: Morphology and Magnetism

Ultrathin magnetic films exhibit extraordinary magnetic properties which are currently exploited in various technical applications. Considerable effort has been devoted to `tailor` the magnetic properties of thin magnetic films such as the magnetic anisotropy, i.e., the orientation of the easy axis of the film magnetization and to limit the magnetic saturation and switching field to levels compatible with practical applications. Among the most promising systems for magneto-electronics, magnetic sensors as well as thin film recording media are material combinations between magnetic cobalt, iron, or nickel films with non-magnetic copper as substrate or spacer layer. Recent research has demonstrated that the film morphology, the interface roughness and the possible alloy formation in these systems have a strong influence on the magnetic properties. Therefore, the control of the smoothness and cleanliness of the films and interfaces at the atomic level is of great importance. This requires a thorough understanding of the relationship between film morphology and the magnetic properties. This knowledge will also provide the basis for designing magnetic thin films for different needs and future applications. The aim of this proposal is to characterize the morphology and its correlation with the magnetic properties of thin iron and nickel films on well defined copper surfaces. The main goal is to explore ways to tune the thin film structure and thereby its magnetic properties. Nanostructured Cu-CuO surfaces and regularly stepped copper substrates will be used to study the influence of an imposed lateral patterning of the substrate on the ordering of the deposited magnetic film. The nucleation and growth of magnetic films will be studied at an atomic scale as a function of the growth parameters (surface temperature and deposition rate). Additionally, the influence of oxygen on the growth mode and film quality will be investigated. The experiments will involve (i) an existing Scanning Tunneling Microscope (STM) capable of providing structural and chemical information at the atomic scale and (ii) Reflectance Difference Spectroscopy (RDS) to characterize the interface morphology and composition together with the magnetic properties via the magneto-optical Kerr effect.