Martensitic transitions in shape memory Ni-Mn-Ga Heusler alloys take place between a high temperature austenite and a low temperature martensite phase. However, intermartensitic transformations have also been encountered that occur from one martensite phase to another. To examine intermartensitic transitions in magnetic shape memory alloys in detail, we carried out temperature dependent magnetization, resistivity, and x-ray diffraction measurements to investigate the intermartensitic transition in Ni₅₀Mn_50–xGa_x in the composition range $12\le x\le 25$ at. %. Rietveld refined x-ray diffraction results are found to be consistent with magnetization and resistivity data. Depending on composition, we observe that intermartensitic transitions occur in the sequences $7\mathrm{M}\to {\mathrm{L}1}_0,\hspace{0.17em}5\mathrm{M}\to 7\mathrm{M}$ , and $5\mathrm{M}\to 7\mathrm{M}\to {\mathrm{L}1}_0$ with decreasing temperature. The L1₀ non-modulated structure is most stable at low temperature.

The composition dependence of magnetic and structural transformations, as well as the temperature and composition dependence of the magnetocrystalline anisotropy, were studied in the martensitic Ni2+xMn1+yGa1+z (x+y+z=0) Heusler alloys. Moving away from the stoichiometric composition, a slight variation, a large reduction, and a marked enhancement, were, respectively, observed for the Curie temperature, the magnetic anisotropy, and the structural (martensitic–austenitic) transformation temperatures.