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C. B. Murray - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of monodisperse cobalt nanocrystals and their assembly into Magnetic Superlattices invited
    Journal of Applied Physics, 1999
    Co-Authors: C. B. Murray
    Abstract:

    High temperature, solution phase reduction of cobalt chloride in the presence of stabilizing agents was employed to produce Magnetic colloids (ferrofluids) of cobalt nanocrystals. We systematically synthesized and isolated nearly monodisperse nanocrystal samples ranging in size from 2 to 11 nm while maintaining better than a 7% std. dev. in diameter. As synthesized cobalt particles are each a single crystal with a complex cubic structure related to the beta phase of elemental manganese (e-Co). Annealing the nanocrystals at 300 °C converts them quantitatively to the more common hexagonal-close-packed crystal form. Deposition of these uniform cobalt particles on solid substrates by evaporation of the carrier solvent results in the spontaneous assembly of two-dimensional and three-dimensional Magnetic Superlattices (colloidal crystals). A combination of x-ray powder diffraction, transmission electron microscopy, and superconducting quantum interference device magnetometry were used to characterize both the d...

  • Synthesis of monodisperse cobalt nanocrystals and their assembly into Magnetic Superlattices (invited)
    Journal of Applied Physics, 1999
    Co-Authors: Shouheng Sun, C. B. Murray
    Abstract:

    High temperature, solution phase reduction of cobalt chloride in the presence of stabilizing agents was employed to produce Magnetic colloids (ferrofluids) of cobalt nanocrystals. We systematically synthesized and isolated nearly monodisperse nanocrystal samples ranging in size from 2 to 11 nm while maintaining better than a 7% std. dev. in diameter. As synthesized cobalt particles are each a single crystal with a complex cubic structure related to the beta phase of elemental manganese (epsilon-Co). Annealing the nanocrystals at 300 degrees C converts them quantitatively to the more common hexagonal-close-packed crystal form. Deposition of these uniform cobalt particles on solid substrates by evaporation of the carrier solvent results in the spontaneous assembly of two-dimensional and three-dimensional Magnetic Superlattices (colloidal crystals). A combination of x-ray powder diffraction, transmission electron microscopy, and superconducting quantum interference device magnetometry were used to characterize both the dispersed nanocrystals and the assembled Superlattices. (C) 1999 American Institute of Physics. [S0021-8979(99)50908-0].

Shouheng Sun - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis of monodisperse cobalt nanocrystals and their assembly into Magnetic Superlattices (invited)
    Journal of Applied Physics, 1999
    Co-Authors: Shouheng Sun, C. B. Murray
    Abstract:

    High temperature, solution phase reduction of cobalt chloride in the presence of stabilizing agents was employed to produce Magnetic colloids (ferrofluids) of cobalt nanocrystals. We systematically synthesized and isolated nearly monodisperse nanocrystal samples ranging in size from 2 to 11 nm while maintaining better than a 7% std. dev. in diameter. As synthesized cobalt particles are each a single crystal with a complex cubic structure related to the beta phase of elemental manganese (epsilon-Co). Annealing the nanocrystals at 300 degrees C converts them quantitatively to the more common hexagonal-close-packed crystal form. Deposition of these uniform cobalt particles on solid substrates by evaporation of the carrier solvent results in the spontaneous assembly of two-dimensional and three-dimensional Magnetic Superlattices (colloidal crystals). A combination of x-ray powder diffraction, transmission electron microscopy, and superconducting quantum interference device magnetometry were used to characterize both the dispersed nanocrystals and the assembled Superlattices. (C) 1999 American Institute of Physics. [S0021-8979(99)50908-0].

W Prellier - One of the best experts on this subject based on the ideXlab platform.

  • direct observation of pinned biased moments in Magnetic Superlattices
    Physical Review B, 2005
    Co-Authors: P Padhan, W Prellier
    Abstract:

    We report the pinned/biased moment in the Superlattices consisting of ferroMagnetic (FM) ${\mathrm{SrRuO}}_{3}$ and antiferromgnetic (AFM) ${\mathrm{SrMnO}}_{3}$. This superlattice system shows anisotropy and oriented pinning/biasing in the field-cooled hysteresis loop. The in-plane cooling field provides antiferroMagnetic orientations, whereas the out-of-plane cooling field provides ferroMagnetic orientations to the pinned/biased moments. The spacer layer thickness, strength, and orientation of Magnetic field, cooling field, and driving current influence the pinning strength. We propose that the Magnetic structure is a repetition of AFM/Pin/FM(Free)/Pin unit below a critical field to explain its Magnetic and transport properties. The transport behavior is discussed using the spin-dependent conduction.

  • Anisotropic pinned/biased magnetization in SrRuO3/SrMnO3 Superlattices
    The European Physical Journal B - Condensed Matter and Complex Systems, 2005
    Co-Authors: P Padhan, W Prellier
    Abstract:

    The exchange coupling at the interfaces of Magnetic Superlattices consisting of ferroMagnetic SrRuO3 and antiferroMagnetic SrMnO3 grown on (001) oriented SrTiO3 is studied with in-plane and out-of-plane orientations of the cooling Magnetic field, with respect to the substrate plane. The magnetization of the in-plane, field cooled hysteresis loop is lower than the corresponding in-plane zero-field-cooled hysteresis loop. The out-of-plane field cooled hysteresis loop is shifted, from the origin, along the graphical magnetization axis. We attribute this irreversible rotation of the moment to the pinning/biasing of spin in the SrRuO3 layer in the vicinity of interfaces by the antiferroMagnetic SrMnO3 layer.

P Padhan - One of the best experts on this subject based on the ideXlab platform.

  • direct observation of pinned biased moments in Magnetic Superlattices
    Physical Review B, 2005
    Co-Authors: P Padhan, W Prellier
    Abstract:

    We report the pinned/biased moment in the Superlattices consisting of ferroMagnetic (FM) ${\mathrm{SrRuO}}_{3}$ and antiferromgnetic (AFM) ${\mathrm{SrMnO}}_{3}$. This superlattice system shows anisotropy and oriented pinning/biasing in the field-cooled hysteresis loop. The in-plane cooling field provides antiferroMagnetic orientations, whereas the out-of-plane cooling field provides ferroMagnetic orientations to the pinned/biased moments. The spacer layer thickness, strength, and orientation of Magnetic field, cooling field, and driving current influence the pinning strength. We propose that the Magnetic structure is a repetition of AFM/Pin/FM(Free)/Pin unit below a critical field to explain its Magnetic and transport properties. The transport behavior is discussed using the spin-dependent conduction.

  • Anisotropic pinned/biased magnetization in SrRuO3/SrMnO3 Superlattices
    The European Physical Journal B - Condensed Matter and Complex Systems, 2005
    Co-Authors: P Padhan, W Prellier
    Abstract:

    The exchange coupling at the interfaces of Magnetic Superlattices consisting of ferroMagnetic SrRuO3 and antiferroMagnetic SrMnO3 grown on (001) oriented SrTiO3 is studied with in-plane and out-of-plane orientations of the cooling Magnetic field, with respect to the substrate plane. The magnetization of the in-plane, field cooled hysteresis loop is lower than the corresponding in-plane zero-field-cooled hysteresis loop. The out-of-plane field cooled hysteresis loop is shifted, from the origin, along the graphical magnetization axis. We attribute this irreversible rotation of the moment to the pinning/biasing of spin in the SrRuO3 layer in the vicinity of interfaces by the antiferroMagnetic SrMnO3 layer.

Jin Sil Choi - One of the best experts on this subject based on the ideXlab platform.

  • Magnetic Superlattices and their nanoscale phase transition effects
    Proceedings of the National Academy of Sciences of the United States of America, 2006
    Co-Authors: Jinwoo Cheon, Jongil Park, Jin Sil Choi
    Abstract:

    The systematic assembly of nanoscale constituents into highly ordered Superlattices is of significant interest because of the potential of their multifunctionalities and the discovery of new collective properties. However, successful observations of such superlattice-associated nanoscale phenomena are still elusive. Here, we present Magnetic Superlattices of Co and Fe3O4 nanoparticles with multidimensional symmetry of either AB (NaCl) or AB2 (AlB2). The discovery of significant enhancement (≈25 times) of ferrimagnetism is further revealed by forming previously undescribed Superlattices of Magnetically soft–hard Fe3O4@CoFe2O4 through the confined geometrical effect of thermally driven intrasuperlattice phase transition between the nanoparticulate components.