Tailoring exchange interactions in engineered nanostructures: an ab initio study.

We present a novel approach to spin manipulation in atomic-scale nanostructures. Our ab initio calculations clearly demonstrate that it is possible to tune magnetic properties of subnanometer structures by adjusting the geometry of the system. By the example of two surface-based systems we demonstrate the following. (i) The magnetic moment of a single adatom coupled to a buried magnetic Co layer can be stabilized in either a ferromagnetic or an antiferromagnetic configuration depending on the spacer thickness. It is found that a buried Co layer has a profound effect on the exchange interaction between two magnetic impurities on the surface. (ii) The exchange interaction between magnetic adatoms can be manipulated by introducing artificial nonmagnetic Cu chains to link them.