Research ArticleGEOPHYSICS

Direct visualization of the thermomagnetic behavior of pseudo–single-domain magnetite particles

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Science Advances  15 Apr 2016:
Vol. 2, no. 4, e1501801
DOI: 10.1126/sciadv.1501801
  • Fig. 1 Visualization of the thermomagnetic behavior of a small PSD Fe3O4 grain (sample G1).

    (A) Bright-field TEM image of the individual Fe3O4 grain (~150 nm in length across its long-diagonal axis), with associated electron diffraction pattern inset. (B to H) Magnetic induction maps reconstructed from holograms taken at (B) 20°C (with the red arrow, labeled FD, showing the direction of the in-plane component of the applied saturating field to induce magnetic remanence, whereas the blue arrow shows the additional direction the field was applied for the calculation of the mean inner potential); during in situ heating to (C) 400°C, (D) 500°C, and (E) 550°C; upon subsequent cooling to (F) 500°C, (G) 400°C, and (H) 20°C. The contour spacing is 0.098 rad for all the magnetic induction maps, and the magnetization direction is shown using arrows, as depicted in the color wheel. v, center of the vortex.

  • Fig. 2 Visualization of the thermomagnetic behavior of a slightly larger PSD Fe3O4 grain (sample G2).

    (A) Bright-field TEM image of an individual Fe3O4 grain (~250 nm in length across its long-diagonal axis), with associated electron diffraction pattern inset. (B to H) Magnetic induction maps reconstructed from holograms taken at (B) 20°C (with the red arrow, labeled FD, showing the direction of the in-plane component of the applied saturating field to induce magnetic remanence, whereas the blue arrow shows the additional direction the field was applied for the calculation of the mean inner potential); during in situ heating to (C) 400°C, (D) 500°C, and (E) 550°C; upon subsequent cooling to (F) 500°C, (G) 400°C, and (H) 20°C. The contour spacing is 0.53 rad for all the magnetic induction maps, and the magnetization direction is shown using arrows, as depicted in the color wheel.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/4/e1501801/DC1

    X-ray diffractometry

    In situ heating within the TEM

    Off-axis electron holography

    fig. S1. X-ray diffraction pattern of the Fe3O4 powder.

    fig. S2. Images of DENSsolutions Wildfire in situ heating holder and EMheaterchips.

    fig. S3. Schematic diagram of the setup for off-axis electron holography.

    fig. S4. Magnetic induction maps of sample G1 at intermediate stages of heating and cooling.

    fig. S5. Magnetic induction maps and proposed 3D forms of vortex states in sample G1.

    fig. S6. Magnetic induction maps of sample G2 at intermediate stages of heating and cooling.

    fig. S7. Magnetic induction maps and proposed 3D forms of vortex states in sample G2.

  • Supplementary Materials

    This PDF file includes:

    • X-ray diffractometry
    • In situ heating within the TEM
    • Off-axis electron holography
    • fig. S1. X-ray diffraction pattern of the Fe3O4 powder.
    • fig. S2. Images of DENSsolutions Wildfire in situ heating holder and EMheaterchips.
    • fig. S3. Schematic diagram of the setup for off-axis electron holography.
    • fig. S4. Magnetic induction maps of sample G1 at intermediate stages of heating and cooling.
    • fig. S5. Magnetic induction maps and proposed 3D forms of vortex states in sample G1.
    • fig. S6. Magnetic induction maps of sample G2 at intermediate stages of heating and cooling.
    • fig. S7. Magnetic induction maps and proposed 3D forms of vortex states in sample G2.

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