Effect of lattice contraction on martensitic transformation and magnetocaloric effect in Ge doped Ni–Mn–Sn alloys

The composition dependences of the structure, martensitic transformation and the magnetocaloric effect in Ni43Mn46Sn11−xGex (x = 0, 1, 2) ferromagnetic shape memory alloys are investigated. These samples all have L21 Heusler type structure at room temperature. With the increase of Ge content, the cell volume decreases, and the martensitic transformation temperatures increase rapidly. Large low-field magnetic entropy changes around the martensitic transformation temperatures are observed. Compared to the conventional way to control martensitic transformation temperatures by the adjustment of valence electron concentration, our results indicate that the adjustment of cell volume provides an alternative way to tailor the martensitic transformation and the magnetocaloric effect in ferromagnetic shape memory alloys.