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Domain Models of Ferromagnetic Shape Memory Materials
Author(s) -
Rößler Ulrich K.
Publication year - 2012
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201200120
Subject(s) - shape memory alloy , materials science , crystal twinning , condensed matter physics , ferromagnetism , martensite , magnetic shape memory alloy , multiferroics , ferroelasticity , diffusionless transformation , lattice (music) , microstructure , magnetic domain , ferroelectricity , crystallography , magnetic field , magnetization , metallurgy , physics , optoelectronics , chemistry , quantum mechanics , acoustics , dielectric
Magnetic shape‐memory materials are multiferroics that combine ferroelastic and ferromagnetic order. The diffusionless transformation processes in these materials unroll by the creation of crystallographic domains or twinned microstructures that are coupled to magnetic domain patterns. Miniaturization of the crystallographic domains to the scale of lattice unit cells is afforded by the concept of adaptive modulated martensite. A ferroelastic model for these crystallographic domain patterns is introduced for the exemplary case of the Ni 2 MnGa Heusler alloy. The pseudo‐microscopic model incorporates data from ab initio calculations and phonon dispersion. The twin‐boundary energy for the diffuse wall of this model are very low of the order 1 mJ · m −2 fulfilling a key requirement for the formation of adaptive martensite in this material. An extension of the Ginzburg–Landau phase‐field model for large strain gradients is introduced to model atomically sharp twin‐boundaries.