Credit: © 2007 AAAS

An understanding and manipulation of the magnetic anisotropy — that is, the preferred direction of magnetization — of single-atom-sized magnetic structures is critical for the realization of ultrahigh-density magnetic storage devices and quantum computing. Nanojunctions are widely used to determine the physical properties of magnetic nanostructures, but such methods do not yield accurate information on the atomic scale. Scanning probes could, however, overcome such limitations.

Now, a multinational team led by Andreas Heinrich from the IBM Research Division at the Almaden Research Center in San Jose in the USA, have for the first time, used scanning tunnelling microscopy (STM) to observe and control the magnetic isotropy of individual atoms on a surface1 . The researchers used the STM tip to deposit iron and manganese atoms on a copper nitride surface, and made differential current measurements at 0.5 K, under magnetic fields up to 7 T. They decoupled the magnetic properties of the Fe and Mn atoms from those of the underlying Cu layer by using an atomic layer of CuN. The magnetic isotropy of the Mn atoms was found to be significantly weaker than Fe on the CuN substrate.

This approach, in which individual atoms are embedded in a surface, shows tremendous potential for the manipulation and study of magnetic anisotropy for single atomic spins.