Details

Autor(en) / Beteiligte

• Gruner, Markus Ernst
• Fähler, Sebastian
• Entel, Peter

Titel

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

Ist Teil von

• Physica Status Solidi. B: Basic Solid State Physics, 2014-10, Vol.251 (10), p.2067-2079

Ort / Verlag

Blackwell Publishing Ltd

Erscheinungsjahr

2014

Quelle

Wiley-Blackwell Full Collection

Beschreibungen/Notizen

• 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. Nanotwinned adaptive microstructures in Ni2 MnGa and Fe68 Pd32 magnetic shape memory alloys obtained from first‐principles calculations. Based on the results of recent first‐principles calculations, Gruner et al. review the role of modulated or adaptive martensites in magnetic shape memory alloys. The authors work out an analogy between two paradigmatic materials classes, Ni2MnGa and Fe70P30, and demonstrate that in both cases the low formation energy for tetragonal twins opens an alternative transformation path which allows the evolution of a functional hierarchical microstructure upon cooling. In turn, finite temperature magnetic disorder destabilizes modulation and adaptive martensite in favor of the cubic austenite pointing out the strong impact of magnetoelastic interactions on the transformation process.