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"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.

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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