Antiferromagnetic nanoparticles: Static and dynamic properties

The magnetic properties of very small particles consisting of only a few thousand of atoms are very different from those of macroscopic samples of the same material. It turns out the the magnetic entities sitting at the surface mostly determine the magnetic behaviour. Since in small particles the proportion of surface to the total number of magnets is high, new features arise when the size of the particles is lowered. These effects have been used to store information on e.g. tapes, hard and floppy disc drives. In this work the time dependent magnetism of such particles are studied theoretically when the external magnetic field is switched off or reversed. If the dependence on the size of the particles is determined, experimental measurements on ensembles of fine magnetic particles can be interpreted accordingly. This will provide a reliable magnetic characterisation and analysis tool with applications also in medical science (targeted drug delivery system involving magnetic steering, imaging using magnetic resonance).