Martensitic transformation and shape memory effect of Ni-rich Ni2MnGa sputtered films under magnetic field

M. Ohtsuka, M. Matsumoto, K. Koike, T. Takagi, K. Itagaki

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The inference of a magnetic field on the martensitic transformation (MT) temperatures and shape memory effect (SME) was investigated for the Ni-rich Ni2MnGa sputtered films. The compositions of the films were Ni51.4Mn28.3Ga20.3, Ni54.1Mn23.0Ga22.9 and Ni54.4Mn21.3Ga24.3. The films were heat treated at 1073 K for 3.6 ks and aged at 673 K for 3.6 ks in a constrained condition. Hereafter, the constraint-aged films were described as N51.4(AG), N54.1(AG) and N54.4(AG) using nickel content, respectively. The reversible two-way SME by the thermal change was confirmed for the all constraint-aged films through the MT and its reversion. The gradient of the strain-temperature curve, the amount of strain accompanied by the two-way SME and the width of thermal hysteresis were dependent on the composition of the films. The strain-temperature curves shifted to a high temperature region and the martensitic phase was stabilized by the magnetic field. The strain at the outer surface was given by ε{lunate}=d/2r, where d was the thickness of the films and r was the radius of a curvature for the films. The increase of MT temperatures caused by a magnetic field was about 1 K/T. Furthermore, the two-way SME by the magnetic field was observed around the MT temperature on cooling for the N54.4(AG) film with the large gradient and small thermal hysteresis in the strain-temperature curve.

Original languageEnglish
Pages (from-to)2782-2784
Number of pages3
JournalJournal of Magnetism and Magnetic Materials
Volume310
Issue number2 SUPPL. PART 3
DOIs
Publication statusPublished - 2007 Mar

Keywords

  • Ferromagnetic shape memory alloy
  • Magnetic-field induced shape memory effect
  • Martensitic transformation
  • NiMnGa
  • Sputtered film

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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