Strain induced spin-gapless semiconductivity in FeCrTiAl

Spin-gapless semiconductors (SGS) represent a new class of materials with potential applications in spin-based electronics. Here, we performed a combined theoretical and experimental study of FeCrTiAl, a quaternary Heuser compound that was recently predicted to exhibit nearly SGS properties. Our calculations indicate that this material undergoes a transition from quasi-SGS to SGS under mechanical expansion (approximately, 4% increase of the lattice constant). At the same time, mechanical compression results in reduced spin-polarization of FeCrTiAl. Potentially, a negative pressure (mechanical expansion) may be achieved either by applying an epitaxial strain in thin-film geometry, or by chemical substitution, e.g. with non-magnetic element of larger atomic radius. Interestingly, further increase of the lattice parameter (~6%) leads to a type-2 to type-1 SGS transition. However, such large values of mechanical strain may be difficult to achieve in practice. Our results may provide guidance for further research on strain induced manipulation of electronic properties of spin-gapless semiconductors.