Point-Group Dependence of Dzyaloshinski-Moriya Micromagnetics

ORAL

Abstract

The micromagnetic realization of Dzyaloshinski-Moriya interactions (DMI) is investigated, with particular reference to spin spirals and skyrmions in crystals with cubic symmetry. The analysis starts with a group-theoretical analysis and explains the micromagnetism by a magnetic gyration tensor that is loosely related to the vector D of the DMI. In contrast to conventional wisdom, the DM free-energy term D M.(▽×M) is not caused by broken inversion symmetry but reflects the presence of chiral building blocks (motifs) in the crystal structure. The scalar D includes not only DMI but also magnetocrystalline and magnetostatic contributions. In micromagnetic calculations, this D should never be used for noncubic structures, such as uniaxial tetragonal, rhombohedral, and hexagonal crystals. Furthermore, D = 0 for the cubic point groups Th, Oh, and Td, which include half- and inverse Heusler alloys (Td), in spite of their broken inversion symmetry and nonzero atomic-scale DMI. The theoretical findings are used to discuss skyrmions in a range of related alloys: MnNiGa and MnNiSn, which crystallize in the centrosymmetric hexagonal Ni2In structure (point group D6h), and Heusler-type cubic compounds MnNiIn and MnNiAl.

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Presenters

  • Ahsan Ullah

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

Authors

  • Ahsan Ullah

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

  • Balamurugan Balasubramanian

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

  • Andrei Sokolov

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

  • Lanping Yue

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

  • Shah Valloppilly

    Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy,, University of Nebraska, Lincoln, Nebraska 68588-0299, USA, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, United States

  • Xingzhong Li <xzli@unl.edu>, Li

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

  • Wenyong Zhnag

    Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy,, University of Nebraska, Lincoln, Nebraska 68588-0299, USA, Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, United States

  • David Sellmyer

    Physics & Astronomy, University of Nebraska, Lincoln, Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy,, University of Nebraska, Lincoln, Nebraska 68588-0299, USA, University of Nebraska - Lincoln, Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, United States

  • Ralph Skomski

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