Magnetic properties of Ni40+xMn39−xSn21 (x = 0, 2, 4, 6 and 8 at.%) Heusler alloys

• Curie temperature versus e/a dependence shows broad maximum in NiMnSn alloys.
• Magnetic moment versus e/a < 7.75 dependence was determined.
• The localized magnetic moment model is compatible with the magnetic moment evolution.
• The values of the magnetic moments indicate an almost full atomic order.

The low electron concentration region (e/a < 7.75) of the magnetic phase diagram of the off-stoichiometric Ni–Mn–Sn Heusler alloys was investigated in detail by DSC and magnetization measurements of the Ni40+xMn39−xSn21(x = 0, 2, 4, 6 and 8 at.%) alloys. The alloys show a stable austenitic phase without any martensitic transformation down to 5 K even after heat treatment. The Curie temperature exhibits a broad maximum over a large composition range. The evolution of the magnetic moment with the electron concentration fits the data of previous studies and confirms the peak-like dependence in the extended range of e/a values predicted by ab initio calculations. The explored part of the moment versus e/a curve can be explained in terms of a localized magnetic moment model and full atomic order in the alloys.