Pressure dependent half-metallic ferromagnetism in inverse Heusler alloy Fe₂CoAl: a DFT+U calculations

We report the electronic and magnetic properties along with the Curie temperature (T _C) of the inverse full Heusler alloy (HA) Fe₂CoAl obtained by using the first-principles computational method. Our calculations suggests that Fe₂CoAl is a magnetic metal when treated within PBE-GGA under the applied compressive pressures. However, the implementation of electron-electron (U) (i.e., GGA+U) with varying compressive pressure (P) drastically changes the profile of the electronic structure. The application of GGA+U along with pressure induces ferromagnetic half-metallicity with an integer value of total magnetic moment ∼4.0 μ _B per unit cell. The integer value is in accordance with the Slater-Pauling's rule. Here, we demonstrate the variation of semiconducting gap in the spin down channel. The band gap increases from 0.0 eV to 0.72 eV when increasing the pressure from 0 to 30 GPa. Beyond 30 GPa, the electronic band gap decreases, and it is completely diminished at 60 GPa, exhibiting metallic behaviour. The analysis of the computed results shows that the treatment of electron-electron interactions within GGA+U and the application of compressive pressure in Fe₂CoAl enables d-d orbital hybridization giving rise to a half-metal ferromagnet. The T _C calculated from mean field approximation (MFA) decreases up to 30 GPa and then increases linearly up to 60 GPa.