1. Nanostructural Evolution and Magnetic Response in the Oxidation of FeCo Nanomaterials. Michael E. McHenry, Carnegie-Mellon University, DMR 0804020 Magnetic nanoparticles (MNPs) are of interest for a range of applications including data storage and biomedicine. FeCo MNPs have high saturation magnetizations making them useful for biomedical applications where small volumes of particles are required which produce larger signals, while FeNi MNPs have tunable Curie temperatures, useful for self-regulated radio frequency heating applications. We have successfully chemically synthesized monodisperse FeCo and FeNi MNPs which have been characterized on the right. (courtesy K. McNerny) TEM image of chemically synthesized FeCo nanoparticles (left); PXRD pattern for FeCo nanoparticles with indexed peaks (lower left); and hysteresis loop showing a saturation magnetization of 252 emu/g of FeCo.

2. Oxidation of Iron-Cobalt Alloys Michael E. McHenry, Carnegie-Mellon University, DMR 0804020 The properties of FeCo alloys are being investigated at elevated temperatures. In particular, their oxidation charateristics are being analyzed to better understand their performance over time. Nanoparticles and thin films of FeCo were made and observed using Transmission Electron Microscopy and other techniques. The layers of oxidation were observed in the thin film cross- section on the top right. This cross- section is overlaid with the composition of the layers. Understanding this layered material is essential to predicting its properties. A mathematical model has been developed to predict the magnetic properties of the thin film with increasing oxide thickness. These energy surface plots are in the bottom right. 0 0.1 0.5 0.05 Cross-section of an oxidized FeCo thin film (top right) compared to compositional analysis using XPS. Magnetic energy surface plots (bottom right) show the minimum energy magnetization direction for an increasing ratio of oxide:FeCo. OxideFeCoCrSi Ta (courtesy N. Jones)

3. This investigation into the oxidation properties of FeCo alloys will help to determine their usability in thermoablative cancer therapy, by understanding the interaction between the various layers of the nanoparticles and how their properties change with increasing oxidation. The oxidation surfaces may also help determine how easily a cancer antibody can be affixed to the nanoparticles before injection into the body. The thin film samples will help to isolate the specific surfaces of interest, and the mathematical modeling will help predict their magnetic properties. Oxidation of Iron-Cobalt Alloys Michael E. McHenry, Carnegie-Mellon University, DMR 0804020 RT200 °C, 2hrs. 350 °C, 2hrs. 900 °C, 2hrs. Oxidized FeCo Nanoparticles (courtesy N. Jones)