Characterization of Epsilon-Co Nanoparticles with Thin Oxide Shells

In order to fully understand the magnetism of nanosystems it is often necessary to characterize an unavoidable thin magnetic metal-oxide shell. This is particularly challenging when the system is comprised of self-assembled nanoparticles that can neither be treated as fully ordered nor randomly distributed, as was the case for our sample which coherently close packs in regions on the micron scale. X-ray powder diffraction was used to determine that the phase of the shell was cobalt monoxide while the core remained epsilon-Co. TEM showed that the particles were spherical with an average diameter of 7 nm [1], and using small angle x-ray diffraction the nearest neighbor distance was placed at 10.3 nm. Anomalous small angle scattering taken at several energies about the Co k-edge was used to separate the contributions of the metallic cores, metal-oxide shells, and nanoparticle packing. From this experiment radial sizes were determined for both core and shell, the details of which will be presented. 1. ``Interaction effects within Langmuir Layers and three-dimensional arrays of epsilon-Co Nanoparticles'' (in press to J. Appl. Phys.)