| 1. |
- Fonnum, Geir, et al.
(författare)
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Characterization of Dynabeads® by magnetization measurements Mössbauer spectroscopy
- 2005
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 293, s. 41-47
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Tidskriftsartikel (refereegranskat)abstract
- X-ray diffraction, SEM analysis, Mössbauer spectroscopy and magnetic measurements were used to characterize three different magnetic beads (Dynabeads®). Maghemite (γ-Fe2O3) is the predominant crystalline phase. The nanoparticles were evenly spread in the beads, and the crystal sizes were in the range of 8 nm. The nanoparticles showed superparamagnetic behaviour. The particle's intrinsic magnetization of about 340 kA/m is typical for nanoparticles of maghemite.
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| 2. |
- Hanson, Maj, et al.
(författare)
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The influence of magnetic anisotropy on the magnetization of small ferromagnetic particles
- 1993
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 5, s. 725-732
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Tidskriftsartikel (refereegranskat)abstract
- The authors calculated the magnetization of small ferromagnetic particles with uniaxial anisotropy. The numerical data were compared with experimental results for a magnetic liquid consisting of small amorphous Fe 0.75C0.25 particles in decalin. From the comparison an anisotropy K approximately=3*105 J m-3 was estimated.
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| 3. |
- Hanson, Maj, et al.
(författare)
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The influence of particle size interactions on the magnetization susceptibility of nanometre-size particles
- 1995
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 7, s. 9269-9277
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Tidskriftsartikel (refereegranskat)abstract
- We studied the magnetic properties of frozen magnetic liquids containing amorphous Fe1-xCx particles. By varying the particle size and concentration, we could separate single particle effects from interactions. In samples containing particles with median diameters 5.0 nm and 3.8 nm and with spontaneous saturation magnetizations 7.1 kA m-1 and 9.2 kA m -1, effects of particle interactions are observed. For 3.2 nm no interactions were observed. In samples with negligible interactions the superparamagnetic blocking temperature increases with the particle size. The effective anisotropy constant increases with decreasing particle size, implying that the anisotropy is enhanced by surface effects.
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| 4. |
- Hanson, Maj, et al.
(författare)
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Zero-field cooled magnetization of amorphous Fe1-xCx particles - field dependence of the maximum
- 1995
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 7, s. 9263-9268
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Tidskriftsartikel (refereegranskat)abstract
- We measured the zero-field cooled magnetization, MZPC of a frozen magnetic liquid with amorphous Fe1-xCx particles. MZFC has a maximum at Tp approximately=20 K, which is interpreted as due to blocking of superparamagnetic relaxation in single particles. The maximum shifts towards higher temperatures with increasing measuring field. The shift is explained by the nonlinear field dependence of the magnetization of particles with a size distribution. At temperatures below Tp the magnetic particles have a coercivity and remanence in good agreement with those expected for an ensemble of non-interacting uniaxial particles with a random distribution of easy axes.
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| 5. |
- Johansson, Christer, et al.
(författare)
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The magnetization of magnetic liquids containing amorphous Fe1-xCx particles
- 1993
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Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 122, s. 125-128
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Tidskriftsartikel (refereegranskat)abstract
- The magnetization of amorphous Fe1-xCx particles in decalin was measured in magnetic fields up to 12 T at temperatures between 10 and 250 K. For particles with a diameter of 3.2 nm, the zero field cooled magnetization has a maximum at 20 K. This is interpreted as a blocking of the superparamagnetic relaxation of single particles.
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| 6. |
- Yu, Changxun, 1983-, et al.
(författare)
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A Combined X-ray Absorption and Mössbauer Spectroscopy Study on Fe Valence and Secondary Mineralogy in Granitoid Fracture Networks : Implications for Geological Disposal of Spent Nuclear Fuels
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:5, s. 2832-2842
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Tidskriftsartikel (refereegranskat)abstract
- Underground repository in crystalline bedrock is a widely accepted solution for long-term disposal of spent nuclear fuels. During future deglaciations, meltwater will intrude via bedrock fractures to the depths of future repositories where O2 left in the meltwater could corrode metal canisters and enhance the migration of redox-sensitive radionuclides. Since glacial meltwater is poor in reduced phases, the quantity and (bio)accessibility of minerogenic Fe(II) in bedrock fractures determine to what extent O2 in future meltwater can be consumed. Here, we determined Fe valence and mineralogy in secondary mineral assemblages sampled throughout the upper kilometer of fractured crystalline bedrock at two sites on the Baltic Shield, using X-ray absorption and Mössbauer spectroscopic techniques that were found to deliver matching results. The data point to extensive O2-consuming capacity of the bedrock fractures, because Fe(II)-rich phyllosilicates were abundant and secondary pyrite was dispersed deep into the bedrock with no overall increase in Fe(II) concentrations and Fe(II)/Fe(III) proportions with depth. The results imply that repeated Pleistocene deglaciations did not cause a measurable decrease in the Fe(II) pool. In surficial fractures, largely opened during glacial unloading, ferrihydrite and illite have formed abundantly via oxidative transformation of Fe(II)-rich phyllosilicates and recently exposed primary biotite/hornblende.
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