The interaction of nanoscale magnetic dipoles has been observed for the first time by researchers in Germany. Unexpectedly, the dipoles were seen to form chains, rather than the zigzag pattern expected from simple dipole interaction. The team believes this surprising outcome may be caused by higher-order interactions between the dipoles – a result that may have implications for the development of future hard-disk drives.
To set up their array of nanomagnets, the researchers, led by Hartmut Zabel, a physicist at the Ruhr-Universität Bochum, cut a regular square lattice from a thin magnetic iron-palladium film using electron beam lithography. The lattice was made up of circular islands, each a mere 150 nm in diameter. This alloy was chosen for its soft nature, as well as the potential to tune its Curie temperature – the temperature below which it becomes ferromagnetic – with varying iron concentrations. Ion beam sputtering was then used to remove the unwanted material from between the islands.