X-ray Studies of Magnetic Nanoparticle Assemblies [electronic resource].
- Washington, D.C. : United States. Dept. of Energy, 2003.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- vp : digital, PDF file
- Additional Creators:
- Stanford Linear Accelerator Center
United States. Department of Energy
United States. Department of Energy. Office of Scientific and Technical Information
- Monodisperse FePt nanoparticles were prepared using high temperature solution phase synthesis. Polymer-mediated layer-by-layer growth leads to precise control of the particle self-assembly. The narrow particle size distribution (σ ≤ 5%) offers the potential for increased data storage density by utilizing a smaller mean particle size and ultimately storage of one bit per individual nanoparticle. We have studied self-assembled multilayers of magnetic FePt nanoparticles. The L1₀ phase of FePt has a very high magnetic anisotropy which allows the magnetization of particles of about 4 nm diameter to be thermally stable at room temperature. Magnetic measurements using vibrating sample magnetometer were combined with X-ray diffraction (XRD) and Near Edge X-ray Absorption Fine Structure (NEXAFS) Spectroscopy to study the annealed FePt nanoparticle assemblies and to optimize annealing conditions. NEXAFS spectra showed that a fraction of the iron in the as-deposited particles was oxidized, and this fraction was reduced by annealing in inert or reducing atmospheres. A very thin layer (<0.4 nm) of oxide surrounding the particle is sufficient to explain the observed spectra. Structural analysis using XRD showed that a minimum temperature of 450 C was required to start the formation of the ordered ferromagnetic phase. Annealing for longer times and at higher temperatures led to higher coercivity and larger fraction of ordered phase but also to the onset of some agglomeration of the nanoparticles.
- Published through SciTech Connect.
Toney, Michael F.
- Type of Report and Period Covered Note:
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