Magnetic properties of nanodots and ultrathin multilayers
Hans Peter Oepen (Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg)

A new method is presented that has the sensitivity to measure magnetization behavior of single nanostructures. It is demonstrated that the technique gives the ability to separate different signals of single nanodots from a small ensemble of structures. Our method is based on the anomalous Hall-Effect and allows for resolving signals from spherical nanoparticles with diameter down to 3.5 nm. The method gives access to magnetic properties of particles in a wide thermal and dynamical range. The potential of the technique is demonstrated utilizing particles that are created from Co films sandwiched by Pt layers.
The interaction of Co/Pt nanodots is studied utilizing a system of four dots. Applying a magnetic field perpendicular to the easy axis of magnetization, the dots are destabilized and become susceptible to thermal excitations. The telegraph noise is measured that reveals the correlated interactions even for large separation of dots. Tuning the geometry of the dot regarding separation and geometry allows for the determination of the fields that act between individual dots.
Recently we have developed a time resolved SEMPA. The state of the art of the experiment is reported and first examples of periodically driven dynamics in microstructures are given.