Magnetoelastic coupling and the formation of adaptive martensite in magnetic shape memory alloys

Authors

  • Markus Ernst Gruner,

    Corresponding author
    1. IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany
    2. Faculty of Physics and Center for Nanointegration, CeNIDE, University of Duisburg-Essen, 47048 Duisburg, Germany
    Search for more papers by this author
  • Sebastian Fähler,

    1. IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany
    2. Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany
    Search for more papers by this author
  • Peter Entel

    1. Faculty of Physics and Center for Nanointegration, CeNIDE, University of Duisburg-Essen, 47048 Duisburg, Germany
    Search for more papers by this author

Abstract

Reviewing the results of recent first-principles calculations, we work out a close analogy between the two paradigmatic classes of magnetic shape memory materials, the ordered Ni2 MnGa Heusler compound and the disordered Fe70 Pd30 alloy. Despite fundamental differences between both systems, we can demonstrate that in both cases the very low formation energy for tetragonal twins on the smallest length scale opens an alternative transformation path into an adaptive hierarchical microstructure which is important for the functional behavior. The low energy of the (101) twin boundary corresponds to a shear instability which is associated to the soft transversal acoustic phonon in both systems. In turn, changes of the energy landscape upon magnetic disorder are responsible for the stability of austenite. This points out the strong influence of magnetoelastic coupling on the transformation process.

pssb201350397-gra-0001

Nanotwinned adaptive microstructures in Ni2 MnGa and Fe68 Pd32 magnetic shape memory alloys obtained from first-principles calculations.

Ancillary