Martensitic Transformation in Ni–Mn–Ga Alloy Under High Magnetic Fields

An effect of magnetic field on the martensitic transformation (MT) temperature in ferromagnetic shape memory Ni49.4Mn27.7Ga22.9 single crystal with the MT temperature 285 K is studied by measuring and theoretical treatment of the magnetization versus temperature dependencies in a wide range of the high magnetic fields higher than saturating one. In this way, a linear approximation of the field dependence of MT temperature was proved for the high-field range. The linear increase of transformation temperature is characterized by the slope of 3.5 × 10^-2 K/kOe. This value is essentially larger than the value 2 × 10^-2 K/kOe reported by GonzalesComas et al. [Phys. Rev. B 60 (1999) 7085–7090] for the Ni49.5Mn25.4Ga25.1 alloy with a low MT temperature. This difference is in an agreement with the predictions of the Landau theory.