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Magnetic Domains and Twin Boundary Movement of NiMnGa Magnetic Shape Memory Crystals
Author(s) -
Neudert Andreas,
Lai Yin Wai,
Schäfer Rudolf,
Kustov Mikhail,
Schultz Ludwig,
McCord Jeffrey
Publication year - 2012
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201200074
Subject(s) - magnetic domain , materials science , magnetic field , magnetic shape memory alloy , condensed matter physics , domain wall (magnetism) , motion (physics) , magnetic force microscope , domain (mathematical analysis) , nuclear magnetic resonance , magnetization , physics , classical mechanics , quantum mechanics , mathematical analysis , mathematics
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.