Get access

Magnetic Domains and Twin Boundary Movement of NiMnGa Magnetic Shape Memory Crystals

Authors

  • Andreas Neudert,

    1. Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 51 01 19, 01314 Dresden, Germany
    Search for more papers by this author
  • Yin Wai Lai,

    1. Institute for Metallic Materials, IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany
    2. Delta Electronics Int'l (Singapore) Pte Ltd, 4 Kaki Bukit Avenue 1, Singapore 417939, Singapore
    Search for more papers by this author
  • Rudolf Schäfer,

    1. Institute for Metallic Materials, IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany
    2. Department of Mechanical Engineering, Institute for Materials Science, Technical University Dresden, 01069 Dresden, Germany
    Search for more papers by this author
  • Mikhail Kustov,

    1. Nanoscale Magnetic Materials – Magnetic Domains, Institute for Materials Science, University of Kiel, Kaiserstraße 2, 24143 Kiel, Germany
    Search for more papers by this author
  • Ludwig Schultz,

    1. Institute for Metallic Materials, IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany
    2. Department of Mechanical Engineering, Institute for Materials Science, Technical University Dresden, 01069 Dresden, Germany
    Search for more papers by this author
  • Jeffrey McCord

    Corresponding author
    1. Nanoscale Magnetic Materials – Magnetic Domains, Institute for Materials Science, University of Kiel, Kaiserstraße 2, 24143 Kiel, Germany
    • Nanoscale Magnetic Materials – Magnetic Domains, Institute for Materials Science, University of Kiel, Kaiserstraße 2, 24143 Kiel, Germany
    Search for more papers by this author

  • The authors gratefully acknowledge funding through the German Science Foundation DFG priority program SPP1239. The authors are very thankful for discussions and contributions from Prof. A. Bogdanov, Dr. S. Fähler, Prof. O. Gutfleisch, Dr. U. Rößler, and Dr. N. Scheerbaum. Special thanks go to AdaptaMat Ltd. for providing high quality magnetic shape memory single crystals.

Abstract

Time-resolved metallographic optical microscopy techniques are used together with magnetic domain imaging to clarify the interaction between magnetic domains and twin boundary (TB) motion in magnetic shape memory NiMnGa single crystals. The magnetic field and stress induced magnetic domain formation is imaged by a magneto-optical indicator film technique. Reversible TB motion is visualized up to high actuation speeds. From domain observation at adjacent crystal surfaces the fundamental volume magnetic processes during strain and field induced TB motions are derived. For magnetic field induced structural reorientations a concurrent absence of magnetic domain wall motion is found. In contrast, for strain induced reorientations processes, a complete rearrangement of the magnetic domain structure by the moving TB is observed. Dynamic actuation experiments on TB motion reveal non-linear time effects on TB mobility. In addition to training effects, the maximum field induced strain increases with actuation speed. Both effects can be interpreted as the interaction of moving twin boundaries with local non-fixed defects. The summarized results provide key information for the understanding of the connection of magnetic and crystallographic domains in magnetic shape memory alloys and for the optimization of devices for future technical applications.

Ancillary