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Berry-Phase Curvature and Hall Effect in Co Nanoparticles

ORAL

Abstract

Berry-phase contributions to electron transport have attracted much attention in recent years. An intriguing example is the topological Hall effect (THE), but analogous phenomena also exist in magnetic nanostructures exhibiting noncoplanar noncollinear spin structures. We investigate the Berry-phase behavior of dense ensembles of Co nanoparticles using experiments and micromagnetic simulations. The nanoparticles, produced by a cluster-deposition method, have an average size of about 16 nm and exhibit magnetocrystalline anisotropy constants of about 3.5 Merg/cm3 at 5 K. Hall resistivity data show a significant THE, which decreases on decreasing temperature from 300 K to 5 K. Our micromagnetic simulations suggest that the competition between exchange and dipole interactions results in vortex-like spin textures, which increases the magnitude of THE at high temperatures. At low temperatures, the spin texture prefers parallel alignment in the nanoparticle core and possibly due to magnetic anisotropy, and a small THE contribution arises only from the surface of the nanoparticles due to inter-particle interactions. The effect of particle size on the topological Hall effect of Co nanoparticles will also be discussed.

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Presenters

  • Ahsan Ullah

    Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy, University of Nebraska-Lincoln

Authors

  • Ahsan Ullah

    Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy, University of Nebraska-Lincoln

  • Balamurugan Balasubramanian

    Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska - Lincoln, Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy, University of Nebraska-Lincoln

  • Rabindra Pahari

    Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska - Lincoln, Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy, University of Nebraska-Lincoln

  • Ralph Skomski

    Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy, University of Nebraska-Lincoln

  • David J Sellmyer

    Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska - Lincoln, University of Nebraska-Lincoln, Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy, University of Nebraska-Lincoln