"Boundary Conditions in Granular Magnetic Nanostructures with Dzyaloshinski- Moriya Interactions"

ORAL

Abstract

Magnetic nanostructures such as compacted ensembles of metallic nanoparticles and melt-spun ribbons often but not always yield a topological Hall-effect contribution caused by the Berry phase of the conduction electrons. Among the experimental systems recently investigated in our group are MnSi, NiMnGa, NiMnIn, and Co-Si, The Berry-phase effect depends on the spin structure, which is strongly affected by real-structure feature such as easy-axis orientation and grain boundaries. Chemical inhomogeneities at grain boundaries yield ▽A terms in the materials equations (partial differential equations), where A is the exchange stiffness. For sharp interfaces, this term corresponds to Erdmann-Weierstrass (EW) boundary conditions. In the presence of Dzyaloshinski-Moriya interactions (D), there are ▽D terms and modifications to the EW condition. The effect of the boundary conditions on spin structure and Berry phase is far-reaching and epitomized by the contrast between Bessel and modified Bessel functions in grains with cylindrical symmetry.

*This research is supported by DOE BES (DE-FG02-04ER46152)

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Presenters

  • Ahsan Ullah

    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska
    • Department of Physics and Astronomy, NCMN, University of Nebraska - Lincoln 68588-0299, USA

Authors

  • Ahsan Ullah

    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska
    • Department of Physics and Astronomy, NCMN, University of Nebraska - Lincoln 68588-0299, USA

  • Balamurugan Balasubramanian

    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska
    • Physics and Astronomy, University of Nebraska, Lincoln
    • Department of Physics and Astronomy, NCMN, University of Nebraska - Lincoln 68588-0299, USA

  • Wenyong Zhang

    • Department of Physics and Astronomy, NCMN, University of Nebraska - Lincoln 68588-0299, USA

  • David Sellmyer

    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska
    • Physics and Astronomy, University of Nebraska, Lincoln
    • Department of Physics and Astronomy, NCMN, University of Nebraska - Lincoln 68588-0299, USA

  • Ralph Skomski

    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska
    • University of Nebraska
    • Physics and Astronomy, University of Nebraska, Lincoln
    • Department of Physics and Astronomy, NCMN, University of Nebraska - Lincoln 68588-0299, USA