Phase transitions in an Ni-Mn-Ga ferromagnetic alloy with allowance for the modulation order parameter

The phase diagram of structural and magnetic transitions in a shape-memory Ni-Mn-Ga ferromagnetic alloy was theoretically studied in terms of the phen omenological Landau theory of phase transitions with allowance for the modu lation order parameter. It was shown that in this case so-called premartens itic and post-martensitic phase transitions related to the appearance of a modulated structure can occur along with martensitic transformations. Throu gh the magnetoelastic interaction, the deformation and modulation order par ameters substantially affect the magnetic phase transitions.