Domain structure and magnetic properties are studied statically and by varying the applied field (static and frequency) using magnetic imaging techniques (Magnetic Force Microscopy, Magneto-Optics in longitudinal or polar Kerr effect).

The Magnetic Force Microscope (MFM) can acquire the domain structure dynamically by varying the magnetic field and/or temperature. This instrument, therefore, allows the displacement of the domain structure to be visualised with the applied magnetic field. A measurement technique has been developed that enables images to be acquired and analysed as the applied magnetic field changes to measure an individual nanostructure's magnetisation process and hysteresis cycles. An example is shown in the figure, where two MFM images of Ni80Fe20 nanodots are produced by electron beam lithography (800 nm diameter). The magnetisation was organised in a typical vortex structure. The two nanodots are characterised by opposite chirality, the direction of which can be controlled and varied by measuring local hysteresis loops with magnetic force microscopy.