Effects of strain on the half-metallicity and spin gapless feature of Ti2YSi (Y = Fe, Co) alloys

Abstract

Half-metals and spin gapless semiconductors (SGSs), which exhibit 100% spin polarization at the Fermi level, are considered important candidates for spintronics. Using first-principles calculations, we have investigated the effects of uniform strain and tetragonal distortion on the half-metallicity and spin gapless feature of inverse Heusler Ti2YSi (Y = Fe and Co) alloys. Results show that for uniform strains, the half-metallicity occurs in the ranges of lattice parameters from 5.938 Å to 6.535 Å for Ti2FeSi and from 5.924 Å to 6.840 Å for Ti2CoSi. Tetragonal distortions over the ranges of −2.0% to +2.5% and −2.6% to +4.1% could destroy the half-metallicity for Ti2FeSi and Ti2CoSi, respectively. On the other hand, Ti2CoSi is an SGS at lattice constants of 5.968–6.023 Å. An interesting finding is that Ti2CoSi reproduces the SGS character with increasing the lattice parameters to 6.784–6.840 Å. Small tetragonal distortions with ±0.2% will destroy the SGS character of Ti2CoSi.