Synthesis, Assembly, and Optical and Transport Studies of Magnetic Nanostructures

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9871849 Metiu We plan to synthesize and assemble dilute magnetic semiconductor nanostructures and study their transport and optical properties by using near field optical microscopy. It is well known that by reducing the size of a semiconductor structure we can affect and control the properties of the electrons in it. We know practically nothing about the way in which this size reduction affects the magnetic properties of these systems, even though we expect these effects to be considerable. We will prepare nanocrystalline "dots" of II-VI semiconductor doped with divalent transition metal ions with magnetic properties (Mn(II), Cr(II), Fe(II) and Cu(II) ). We can thus study the effect of confinement on the exchange interactions and the magneto-optical properties of these materials. We plan to use a near field microscope to perform femtosecond and cw studies of the magneto-optical properties of individual dots and to determine how these properties depend on dot sizes. We also plan to create ensembles of such dots so that we can study the collective effects created by the interaction between the dots. One of our most important tools is the near field optical microscope. This is a wonderful tool with many exciting uses, but the quantitative interpretation of the measurements is hampered by the lack of a quantitative theory of the electromagnetic fields produced in the structure being studied. We propose to develop new theoretical methods for solving this problem. %%% The kind of studies proposed here are motivated by the need of making smaller electronic devices and denser computer memories. As the elements of these devices become smaller the properties of the electrons in them are being modified. We cannot design these devices if we cannot anticipate and understand how the electrons in them will behave. Our work hopes to fill this gap in our understanding. The ultimate computer will be a device in which the electrons themselves are computing elements. The main candidates right now are systems in which various spin states are being excited, since they maintain the information imparted to them (coherence) for the longest time. This is one additional reason why the study of spin behavior in small structures may impact future technologies. This award is being supported by the Office of Multidisciplinary Activities; the Division of Materials Research, Directorate for Mathematical and Physical Sciences; and the Division of Electrical and Communications Systems, Directorate for Engineering.***