Exploring spin-gapless semiconducting properties of FeVTaAl and FeCrZrAl

In this work, we present results of a computational study of electronic, magnetic, and structural properties of FeVTaAl and FeCrZrAl, quaternary Heusler compounds exhibiting nearly spin-gapless semiconducting properties. Our calculations indicate that these alloys may crystallize in regular Heusler cubic structure, which has a significantly lower energy than the inverted Heusler cubic phase. Both materials exhibit ferromagnetic alignment, with an integer magnetic moment per unit cell at equilibrium lattice parameter. While both FeVTaAl and FeCrZrAl have been reported recently to exhibit spin-gapless semiconducting electronic structure, a closer inspection of their electronic band structures shows that FeVTaAl is a half-metal, while FeCrZrAl is magnetic semiconductor at their equilibrium lattice parameters. Our calculations indicate that while expansion of the unit cell enhances these properties for both compounds, mechanical pressure ultimately destroys half-metallicity of FeVTaAl and magnetic semiconductivity of FeCrZrAl. Thus, both of these materials may be potentially useful for practical applications in spin-based electronics, but one should avoid implementing them in situations where their unit cell volume may be reduced, e.g. in thin-film applications with substrates of larger lattice constants. We hope that these results will stimulate experimental efforts to synthesize these materials.