Kinetic arrest of atomic diffusion-induced spin gapless semiconductor in Ti₂MnAl Heusler compound

The phase stability of the Ti2MnAl Heusler compound was theoretically investigated using first-principles calculations. The formation mechanisms of non-magnetic Ti2MnAl in Cu2MnAl-type structure and spin gapless semiconductor in Ti2MnAl with Hg2CuTi-type structure were revealed. It was found that the kinetic arrest of atomic diffusion during sample preparation from the high-temperature relatively low-symmetric phase to the low-temperature high-symmetric phase resulted in the metastable spin gapless semiconductor in the Ti2MnAl film sample. We propose that interatomic orbital hybridization is responsible for the atomic configuration and consequent phase stability in Ti2MnAl. The investigations suggest that interatomic orbital hybridization is the inherent parameter to designing candidate materials for spin electronic devices, which can be tuned by careful control of the kinetic diffusion process when preparing samples. Owing to the light atoms involved, the effect of spin-orbit coupling on the band structure in spin gapless semiconductor Ti2MnAl is relatively weak. This study will be helpful for the exploration and design of novel functional magnetic materials in the Heusler family.