First-principles investigation of the structure, stability, and magnetic properties of the Heusler alloy Fe2MnSn

Considering the vast compositional space of Heusler alloys, first-principles-based calculations are ideally suitable for predicting the ground state structure and tailoring the magnetic properties of these alloys. We perform density-functional-theory-based calculations for step-by-step identification of the most stable phase of ${\mathrm{Fe}}_{2}\mathrm{MnSn}$, taking into account all the different structural phases exhibited for this alloy (viz., cubic $\mathrm{L}{2}_{1}$, cubic XA, tetragonal $\mathrm{L}{2}_{1}$, tetragonal XA, and hexagonal ${\mathrm{D}0}_{19}$), followed by the calculations of magnetic properties. We identify the magnetic ground state of each phase and then the most stable structural phase by taking into account electronic and geometric relaxation, spin polarization, and vibrational free energy contributions. The ferromagnetic configuration of all the phases is found to be energetically the most favorable magnetic state, while the ferromagnetic hexagonal phase is identified to be the stable structural phase of ${\mathrm{Fe}}_{2}\mathrm{MnSn}$, with a sizable magnetization of $6.45\phantom{\rule{0.28em}{0ex}}{\textmu{}}_{B}/\mathrm{f}.\mathrm{u}.$ Furthermore, the exchange interactions in the hexagonal phase are calculated using the Liechtenstein approach, and this phase shows a high Curie temperature of 729 K attributed to the strong Fe-Fe exchange coupling. The stable hexagonal phase reveals an in-plane magnetic anisotropy of $\ensuremath{-}1.24 \mathrm{MJ}/{\mathrm{m}}^{3}$. The large magnetization and high Curie temperature of this phase can make this material suitable for desired magnetic applications. Computational investigations such as this one, in addition to being a cost effective pathway, may provide many valuable insights for the experimental realization and application of a given alloy.