This paper presents an overview of the characterization and modeling of single crystal ferromagnetic shape memory Ni–Mn–Ga. A continuum thermodynamics model is presented which describes the magnetomechanical characterization of single crystal Ni–Mn–Ga for the following behavior: (i) sensing effect; (ii) actuation effect; (iii) blocked force (stress generation). The thermodynamic potentials, namely the magnetic Gibbs energy and the Gibbs energy, are obtained from the Helmholtz energy in order to arrive at the set of required independent and dependent variables; the potentials include magnetic energy consisting of Zeeman, magnetostatic and anisotropy components, and mechanical energy consisting of elastic and twinning components. Mechanical dissipation and the microstructure of Ni–Mn–Ga are incorporated in the continuum model through the internal state variables volume fraction, domain fraction, and magnetization rotation angle. The constitutive response of the material is obtained by restricting the process through the second law of thermodynamics. The model requires only seven parameters identified from two simple experiments. Several interesting characteristics of Ni–Mn–Ga are examined in concert with the magnetomechanical characterization.
N.N. SARAWATE and M.J. Dapino, “Magnetomechanical characterization and unified energy model for quasistatic behavior of ferromagnetic shape memory Ni-Mn-Ga,” Smart Materials and Structures, Vol. 19, 035001, 22 January 2010.