A5067778295- Characterization and Applications of Magnetic Nanoparticles
- Iron oxide chemistry and applications
- Magnetic properties of thin films
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Theoretical and Computational Physics
- Geomagnetism and Paleomagnetism Studies
- Superconducting Materials and Applications
- Radiation Therapy and Dosimetry
- Magneto-Optical Properties and Applications
- Diamond and Carbon-based Materials Research
- Magnetic Properties and Synthesis of Ferrites
- Geophysical and Geoelectrical Methods
- nanoparticles nucleation surface interactions
- Magnetic Properties of Alloys
- Metallic Glasses and Amorphous Alloys
- Nanomaterials for catalytic reactions
- Transition Metal Oxide Nanomaterials
- Pigment Synthesis and Properties
- Rare-earth and actinide compounds
- Advanced Materials Characterization Techniques
- High-pressure geophysics and materials
- Advanced Chemical Physics Studies
- Gyrotron and Vacuum Electronics Research
- Geochemistry and Geologic Mapping
Danfoss (Denmark)
2006
Technical University of Denmark
1994-2003
Freie Universität Berlin
1995
Bangor University
1993
University of Wisconsin System
1991
University of Wisconsin–Madison
1991
Nanoparticles of metallic iron on carbon supports have been studied insitu by use M\"ossbauer spectroscopy. The magnetic anisotropy energy constant increases with decreasing particle size, presumably because the influence surface anisotropy. Chemisorption oxygen results in formation a layer hyperfine fields similar to those thicker passivation layers, and ferromagnetic coupling spins core particles. In contrast, layers noncollinear spin structure.
The magnetic properties of hematite $(\ensuremath{\alpha}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3})$ particles with sizes about 16 nm have been studied by use M\"ossbauer spectroscopy, magnetization measurements, and neutron diffraction. nanoparticles are weakly ferromagnetic at temperatures least down to 5 K a spontaneous that is only slightly higher than bulk hematite. At $T\ensuremath{\gtrsim}100\mathrm{K}$ the spectra contain doublet, which asymmetric due relaxation in presence an...
The dynamics of a magnetic particle system consisting ultrafine Fe-C particles monodisperse nature has been investigated in large time window, ${10}^{\ensuremath{-}9}--{10}^{4}\mathrm{s}$, using M\"ossbauer spectroscopy, ac susceptibility, and zero field cooled relaxation measurements. By studying two samples from the same dilution series, with concentrations 5 $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\mathrm{vol}%$, respectively, it found that dipole-dipole interaction...
The spin-canting effect has been studied in samples of maghemite particles with the same width about 100 nm, but different length and degree cation disorder. Mössbauer spectra obtained at 5 K a magnetic field 4 T applied parallel to propagation direction gamma rays showed that there is correlation between structural disorder effect. results show observed spin canting not surface effect, atoms interior can be significantly influenced by effects.
Samples of nanoparticles hematite (α-Fe2O3) with average size between 6 and 27 nm have been studied by use Mössbauer spectroscopy. The superparamagnetic relaxation was analysed on the basis Néel-Brown expression for time, τ = τ0 exp[KV/kT]. It found that value increases increasing particle volume, V, whereas magnetic anisotropy energy constant, K, decreases. electric quadrupole interaction, isomer shift hyperfine field extrapolated to 0 K were be essentially independent size.
We present the first triple-axis neutron scattering measurements of magnetic fluctuations in nanoparticles using an antiferromagnetic reflection. Both superparamagnetic relaxation and precession modes $\ensuremath{\sim}15\mathrm{nm}$ hematite particles are observed. The results have been consistently analyzed on basis a simple model with uniaxial anisotropy N\'eel-Brown theory for relaxation.
Carbon-supported metallic iron particles with an average diameter of 3.7 nm have been studied in situ by Mossbauer spectroscopy the temperature range 5-305 K and external magnetic fields up to 4 T. Depending on preparation conditions various amounts amorphous Fe-C are also formed. The hyperfine surface atoms alpha -Fe significantly larger than that bulk at 5 K, but decrease much faster increasing field. superparamagnetic blocking for is about 70 after oxidation it decreases 50 indicating...
A sample with an orientational magnetic texture was prepared by freezing a ferrofluid containing maghemite particles in field. The degree of alignment the easy directions obtained field-cooling examined Mossbauer spectroscopy for varying strengths We compare results predictions simple model assuming that intrinsic anisotropy is uniaxial and are non-interacting. Good agreement between experimental theoretical found. This allows determination energy constant particles, which important...
A proof-of-principle experiment (POPE) has been conducted to demonstrate the stability and operation of superconducting magnetic energy storage (SMES) conductor in an engineering test model (ETM) design. The experimental facility includes: a 100-kA DC power supply; 4-T, 1-m bore, background field split solenoid: three-turn-1-m-diameter coil for ETM conductor; dewar solenoid coil, at 1.8 K 1 atm; support systems vacuum, helium supply recovery, data acquisition. exactly duplicates electric,...
The change in crystal size during high-energy ball-milling of hematite and zinc sulphide powders with initial average 8 nm 4 nm, respectively, has been investigated by X-ray powder diffraction transmission electron microscopy. It is found that the increases time. This result shows steady-state grain experiments bigger particles can be explained an equilibrium between fracturing growth. kinetics growth nanoparticles discussed reference to a simple empirical model.
We present inelastic neutron scattering studies of 4 nm maghemite nanoparticles. In applied magnetic fields (1-4 T) at 300 K, we observe a clear signal from collective excitations (spin precession the whole particle moment). The is coherent since it antiferromagnetic wave vector transfer, 1.31 Å−1. At high fields, frequency varies linearly with field, corresponding to Landé factor g = 2.03(2). intensity temperature (in range 6-300 K) and field in quantitative agreement simple thermodynamic...