Magnetic domain structures in Co-Ni-Al shape memory alloys studied by Lorentz microscopy and electron holography

Yasukazu Murakami, D. Shindo, K. Oikawa, R. Kainuma, K. Ishida

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98 Citations (Scopus)


Magnetic domain structures in recently developed Co-Ni-Al ferromagnetic shape memory alloys were examined by Lorentz microscopy and electron holography, and relations of the martensite variants (crystallographic domains) and the magnetic domains were discussed. Direct observations of the magnetic domain walls by Lorentz microscopy and the magnetic lines of force by electron holography revealed that each martensite variant was divided into fine magnetic domains under a low magnetic field, e.g. about 0.2 mT. Although an applied magnetic field of about 0.4 T made each variant a large single magnetic domain, a similar configuration of multiple magnetic domains to the previous one appeared when the applied field was removed. In situ Lorentz microscopy studies have demonstrated that magnetic domain structures are sensitive to the crystal structure and/or microstructure in Co-Ni-Al alloys, i.e. a magnetic domain structure favorable to the parent phase is not inherited to the parent phase, but a distinct domain structure is observed in the martensitic phase.

Original languageEnglish
Pages (from-to)2173-2184
Number of pages12
JournalActa Materialia
Issue number8
Publication statusPublished - 2002 May 8


  • Electron holography
  • Lorentz microscopy
  • Magnetic domain
  • Magnetic field
  • Martensitic phase transformation
  • Shape memory alloys

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys


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