Prediction of metallic and half-metallic structure and elastic properties of Fe2Ti1−xMnxAl Heusler alloys

Detailed studies of structural and elastic properties of Fe2Ti1−xMnxAl Heusler alloys were carried out using density functional theory within the generalized gradient approximations. In each Heusler alloy, calculations of lattice constants were repeatedly done for successive increases in the lattice constants and the corresponding total energies were recorded. The graphs of the total energy as a function of lattice constant yielded parabolic curves. The present calculations revealed that among the doped alloys, Fe2TiAl and Fe2Ti0.75Mn0.25Al exhibit transitions of electrons from valence to conduction bands thereby making these alloys metallic. On the other hand, the ternary and quaternary alloys (Fe2MnAl and Fe2Ti0.25Mn0.75Al respectively) possess half-metallic behavior with direct band gaps of 0.56 eV and 0.41 eV respectively at the Γ-point in the minorities states. To determine the stability of these alloys, the three independent elastic constants in cubic structures (that included C11, C12, and C44 respectively) were obtained for all the compositions that confirmed their stabilities. The structural and elastic properties calculations confirmed the stabilities of Fe2Ti0.25Mn0.75Al and Fe2MnAl as some new half-metallic materials that can be applicable in spintronic devices. This work revealed the brittleness nature of Fe2TiAl and Fe2MnAl alloys.