We report here a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline materials with accurate size and interface control with improved mechanical and magnetic properties. Using this method, single domain nanocrystalline Fe and Ni particles in 5–10 nm size range embedded in amorphous alumina as well as crystalline TiN have been produced. By controlling the size distribution in confined layers, it was possible to tune the magnetic properties from superparamagnetic to ferromagnetic behavior. Magnetic hysteresis characteristics below the blocking temperature are consistent with single-domain behavior. The paper also presents our results from investigations in which scanning transmission electron microscopy with atomic number contrast (STEM-Z) and energy loss spectroscopy (EELS) were used to understand the atomic structure of Ni nanoparticles and interface between the nanoparticles and the surrounding matrices. It was interesting to learn from EELS measurements at interfaces of individual grains that Ni in alumina matrix does not from an ionic bond indicating the absence of metal-oxygen bond at the interface. The absence of metal-oxygen bond, in turn, suggests the absence of any dead layer on Ni nanoparticles even in an oxide matrix.
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Processing and Properties of Nanostructured Magnetic Materials
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Kumar, D, Yarmolenko, S, Sankar, J, Narayan, J, Tiwari, A, Zhou, H, Jin, C, Kvit, AV, Pennycook, SJ, & Lupini, A. "Processing and Properties of Nanostructured Magnetic Materials." Proceedings of the ASME 2002 International Mechanical Engineering Congress and Exposition. Materials: Processing, Characterization and Modeling of Novel Nano-Engineered and Surface Engineered Materials. New Orleans, Louisiana, USA. November 17–22, 2002. pp. 261-267. ASME. https://doi.org/10.1115/IMECE2002-39364
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