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Download Exchange Interactions Dipolar Interactions Competition between exchange and dipolar interactions leads to domain formation Atom Magnetic Domains

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  • Slide 1
  • Exchange Interactions Dipolar Interactions Competition between exchange and dipolar interactions leads to domain formation Atom Magnetic Domains
  • Slide 2
  • Vary Spacing Vary Size Vary Ordering Magnetic Nanoparticle Arrays
  • Slide 3
  • Fe synthesized using air free solution chemistry methods Thermal decomposition of Fe(CO) 5 in octyl ether Particles coated with surfactant Washed with ethanol and dispersed in hexane D. F. Farrell, S. A. Majetich, and J. P. Wilcoxon, J. Phys. Chem. 107, 11022-11030 (2003). Nanoparticle Synthesis
  • Slide 4
  • 7.0 0.8 nm 9.2 0.7 nm Seeded with Pt (Fe:Pt ~1000:1) Heterogeneously Nucleated Fe
  • Slide 5
  • 9.1 0.9 nm 11.2 1.0 nm 19 nm No Pt salt, larger amount of oleic acid surfactant Homogeneously Nucleated Fe
  • Slide 6
  • Heterogeneous Homogeneous Fe oxide rings dominate Electron Diffraction
  • Slide 7
  • Heterogeneously Nucleated Homogeneously Nucleated 2 Blocking Ts: Fe, Fe oxide H = 200 Oe Field-cooled, Zero field-cooled Magnetization 7.0 0.8 nm 11.2 1.0 nm 0.01vol. % Blocking Temperatures
  • Slide 8
  • Particle Concentration Nucleation Method Fe conc.Particle Diameter #Particles per mL Heterogen.0.051 M5.8 0.5 nm 3.6 Heterogen.0.0957 M7.2 0.5 nm 3.5 Heterogen.0.614 M8.6 1.6 nm 1.3 Heterogen.0.81 M8.4 1.0 nm 1.9 Homogen.0.0284 M11.2 1.0 nm----- Found from calibrated x-ray fluorescence of solutions* Use to determine total mass of Fe s * Dr. Jess P. Wilcoxon, Sandia National Laboratories
  • Slide 9
  • Oxide Shell Thickness Relate s of particles to weighted average of s of Fe core and M s of oxide shell s,part m part = s,core m core + s,shell m shell Diameter ss Fe coreOxide shell 7.0 0.7 nm heterogeneous 175 emu/g5.8 nm0.6 nm 9.2 0.7 nm heterogeneous 175 emu/g8.4 nm0.4 nm 11.2 1.0 nm homogeneous 110 emu/g7.0 nm2.1 nm
  • Slide 10
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