Ab initio calculations of half-metallic ferromagnetism in Cr-doped MgSe and MgTe semiconductors

The full-potential linear-augmented-plane-waves plus local-orbitals (FP-LAPW+lo) method has been employed for investigation of half-metallic ferromagnetism in Cr-doped ordered zinc-blende MgSe and MgTe semiconductors. Calculations of exchange and correlation (XC) effects have been carried out using generalized gradient approximation (GGA) and orbital independent modified Becke-Johnson potential coupled with local (spin) density approximation (mBJLDA). The thermodynamic stability of the compounds and their preferred magnetic orders have been analyzed in terms of the heat of formation and minimum total energy difference in ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering, respectively. Calculated electronic properties reveal that the Cr-doping induces ferromagnetism in MgSe and MgTe which gives rise to a half-metallic (HM) gap at Fermi level (EF). Further, the electronic band structure is discussed in terms of s (p)-d exchange constants that are consistent with typical magneto-optical experiment and the behavior of charge spin densities is presented for understanding the bonding nature. Our results demonstrate that the higher effective potential for the spin-down case is responsible for p-d exchange splitting. Total magnetic moment (mainly due to Cr-d states) of these compounds is 4µB. Importantly, the electronic properties and HM gap obtained using mBJLDA show remarkable improvement as compared to the results obtained using standard GGA functional.