Zagorodniuk S. Magnetoelastic model of ferromagnetic martensites Ni-Mn-Ga

In the present thesis the magnetic and magneto-deformational properties of ferromagnetic Ni-Mn-Ga martensites have been studied. The analytic expression for the magnetic anisotropy energy has been found in the framework of magnetoelastic model. The experimentally observed anomalies being inherent to the temperature dependencies of magnetization of the Ni-Mn-Ga alloys have been described quantitatively. The theoretical magnetization curves have been plotted for the symmetric directions of magnetic field and different martensitic phases that are inherent to the Ni-Mn-Ga alloys. The analytic expressions for the magnetically induced deformation value under the magnetic field applied in [110] and [001] directions are presented. The non-quadratic character of the experimental dependence of magnetization value on the field value is explained.