Enhanced Curie temperature and spin polarization in Co -based compounds under pressure: A first principles investigation

In the present study, we report a systematic first principles study which investigates and tunes the percentage of spin polarization in few Co-based full Heusler alloys Co2CrX (X = Al, Ga and In) under hydrostatic strain. At ambient condition, Co2CrAl exhibits half metallic nature while Co2CrGa possesses nearly half metallic nature and Co2CrIn shows metallic nature. Mechanical and dynamical stabilities of all the investigated compounds are confirmed using elastic tensor analysis and phonon dispersion plots respectively at ambient as well as under compression. Hydrostatic compressive strain is applied to all the systems and Co2CrGa turned out to be a half metal at compressive strain corresponding to V/V0 = 0.85 with 100% spin polarization and the percentage of spin polarization for Co2CrIn gets enhanced as a function of compressive strain. Further, an electronic topological transition (ETT) is also observed in Co2CrGa as a function of compressive strain corresponding to V/V0 = 0.85, driving the system towards the half-metallic nature. In addition, ferromagnetic nature of all these compounds is explained by the exchange interactions at both ambient and under compression. Also, the positive pressure dependence of Curie Temperature (TC) as a function of V/V0 for all the compounds is studied and the highest TC = 646.1 K for Co2CrAl is observed under compression corresponding to V/V0 = 0.85. © 2020 Elsevier Masson SAS