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Ni-Mn-Ga

 

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The effect of magnetic field induced twin boundary motion was first discovered in 1996 on a Ni-Mn-Ga single crystal. Figure A shows an orientation map (~1x1mm² area) of such a single crystal, imaged by the electron back-scatter diffraction method (EBSD). The structural domains (twin variants) with different crystallographic orientation (represented by different colors) are separated by straight and, most importantly, mobile twin boundaries (thin black lines). Magnetic field-induced twin boundary motion generates typical jumps in magnetic field dependent magnetisation measurements. Such jumps are shown in figure B for a polycrystalline fibre. The fibre consist of several grains along the fibre axis (figure C). Magnetic field-induced twin boundary motion was proven in the polycrystalline fibre by EBSD (figure D, URL).

 

Ni-Mn-Ga
EBSD on NiMnGa fibre

 

Ni-Mn-Ga: EBSD orientation map of a single crystal (A). Magnetisation vs. magnetic field curves (B) of a polycrystalline fibre. SEM image and EBSD orientation map of a polycrystalline fibre (C). Proof of magnetic field-induced twin boundary motion in polycrystalline fibre by EBSD (D).

 

Related publications

  • N. Scheerbaum, O. Heczko, J. Liu, D. Hinz, L. Schultz, O. Gutfleisch: Magnetic field-induced twin boundary motion in polycrystalline NiMnGa fibres, New Journal of Physics 10 (2008) 73002/1-8. URL

  • M. Thomas, O. Heczko, J. Buschbeck, U.K. Roessler, J. McCord, N. Scheerbaum, L. Schultz, S. Faehler: Magnetically induced reorientation of martensite variants in constrained epitaxial NiMnGa films grown on MgO(001), New Journal of Physics 10 (2008) 23040/ 1-20. URL

  • K. Mandal, D. Pal, N. Scheerbaum, J. Lyubina, O. Gutfleisch: Magnetocaloric effect in NiMnGa alloys, IEEE Transactions on Magnetics 11 (2008) 2993-2996.
  • N. Scheerbaum, D. Hinz, O. Gutfleisch, K.-H. Mueller, L. Schultz: Textured polymer bonded composites with NiMnGa magnetic shape memory particles, Acta Materialia 55 (2007) 2707-2713. URL
  • N. Scheerbaum, D. Hinz, O. Gutfleisch, W. Skrotzki, L. Schultz: Compression-induced texture change in NiMnGa-polymer composites observed by synchrotron radiation, Journal of Applied Physics 101 (2007) 9C501/1-3. URL
  • D. Hinz, N. Scheerbaum, O. Gutfleisch, K.-H. Mueller, L. Schultz: Polyester-bonded textured composites with single-crystalline shape memory NiMnGa particles, Journal of Magnetism and Magnetic Materials 310 (2007) 2785-2787. URL

  • Y.W. Lai, N. Scheerbaum, D. Hinz, O. Gutfleisch, R. Schaefer, L. Schultz, J. McCord: Absence of magnetic domain wall motion during magnetic field induced twin boundary motion in bulk magnetic shape memory alloys, Applied Physics Letters 90 (2007) 192504/1-3. URL

 

 

 

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