The structural stability and magnetic properties of the ferromagnetic Heusler alloy Ni-Mn-Sn: A first principle investigation

The phase stability and magnetic properties of the cubic phase L21 and modulated four- and five-layered orthorhombic (4O, 5M) and unmodulated tetragonal (L10) martensite of Ni-Mn-Sn alloys are investigated using the first-principle calculations. The results show that for Ni2Mn1+xSn1−x the martensite phases can be stable only at x≥0.05. The stability of L21 phase decreases while it increases for L10 with the increasing of Mn contents. The anti-ferromagnetic order is stable for both L21 and martensite phases. The modulated 5M and 4O structures are determined accurately and the displacement of the atoms exhibits a sine-like oscillation along the stacking direction. Furthermore, a regular oscillation can also be observed in the distribution of the magnetic moments. With the analysis of the electronic structures, the origin of the effect of the modulation on the system can be explained. The modulation induced displacement of the atoms enhances the charge accumulation between the Ni and Mn/Mn', which lead to a stronger interaction and more structural stability. Accordingly, the calculated results may help in gaining the comprehensive and detailed information on the structural and magnetic properties of the modulated martensite structures, for better understanding of the basic transformation in Ni-Mn-Sn alloys.