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  • 1
    Electronic Resource
    Electronic Resource
    On spin-canting in maghemite particles : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6583-6585 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The degree of alignment of the magnetic moments of Fe3+ ions in ultrafine maghemite particles has been studied in samples with induced magnetic texture. The textured samples were prepared by freezing ferrofluids, containing 7.5 nm maghemite particles, in a magnetic field. Mössbauer spectroscopy studies of the textured samples in large magnetic fields demonstrate that the lack of full alignment is not an effect of large magnetic anisotropy, as suggested recently, but that the effect is rather due to canting of individual spins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356902
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Properties of amorphous FeCoB alloy particles (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5508-5508 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous and crystalline alloy particles (0.05–0.5 nm) of FexCoyBz in which the ratio x:y ranges from 0 to 1 have been prepared by the borohydride reduction of iron and cobalt salts in aqueous solution. The structure of the particles has been studied using Mössbauer spectroscopy and x-ray diffraction. Magnetic measurements of the saturation magnetization, coercivity, and remanence of the particles have been measured. The transition from the amorphous-to-crystalline state has been studied using differential scanning calorimetry (DSC) and thermomagnetometry up to a temperature of 450 °C (see Fig. 1). It has been shown that the fraction of boron in the alloys (10–35 at. %) is dependent upon the rate of addition of salts to borohydride and the concentration of cobalt present; this in turn influences the crystallinity and magnetic properties .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342317
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  • 3
    Electronic Resource
    Electronic Resource
    Remanence curves of cobalt ferrite powders obtained by fractionation of a suspension through a silica gel column (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5840-5842 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magnetic ink has been prepared which consists of a colloidal suspension of cobalt particles of ∼10-nm median diameter of the volume fraction. Gel filtration techniques have been used to separate the particles into a number of fractions of different particle size. Isothermal remanent magnetization (IRM) curves have been plotted for each fraction in the dried state. The maximum value of IR/IS (remanence/saturation magnetization) is 0.5 equal to a value for a distribution of uniaxial particles with easy axes randomly oriented. This value is well below the value of 0.8 expected for cobalt ferrite which has cubic crystalline anisotropy. All fractions, except for those containing the largest particles, have values of IR/IS 〈0.5 due to the presence of superparamagnetic particles. The experimental points on the IRM curves have been fitted to theoretical curves derived from a model by Chantrell et al.7 for a system of uniaxial particles with axes randomly oriented and containing a lognormal distribution of particle volume. Using a value of anisotropy constant K=1.8×105 J m−3 obtained from measurement of the decay of remanence with temperature, satisfactory agreement between particle size determined experimentally and that used in the model has been obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342225
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal conductivity measurements on ferrofluids (1982)
    Springer
    Colloid & polymer science 260 (1982), S. 333-338 
    Details
    ISSN: 1435-1536
    Keywords: Magnetic fluids ; Thermal conductivity ; Colloidal Fe3O4 particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The thermal conductivity of a number of ferrofluids consisting of colloidally dispersed Fe3O4 particles in diester, hydrocarbon, water and fluorcarbon carriers have been measured at 38°C. The variation in thermal conductivity with particle concentration is well described by Tareef's equation (1940). This has enabled the ratio of the physical to magnetic size to be determined and compared with estimates of the ratio obtained from electron micrographs and magnetic measurements. The fit between theory and experiment is particularly good for hydrocarbon carrier fluids giving the ratio of solid to magnetic radiusR i/R m=1.24±0.03 compared with the value obtained from magnetic data and electron micrographs of 1.19±0.07. The corresponding value from the fluids with a diester carrier ranges between 1.1〈R d/R m〈1.3 which is again consistent with microscopy and magnetic data. The application of a magnetic field of 0.1 T had no noticeable effect on the thermal conductivities of ferrofluids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01447973
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  • 5
    Electronic Resource
    Electronic Resource
    The structure of magnetic particles studied by small angle neutron scattering (1981)
    Springer
    Colloid & polymer science 259 (1981), S. 395-397 
    Details
    ISSN: 1435-1536
    Keywords: Cobalt ferrofluids ; Magnetic Liquids ; Neutron Scattering ; Colloidal cobalt particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01524721
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    Paper (German National Licenses)
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