First principles density functional calculations of half-metallic ferromagnetism in Zn1-xCrxS and Cd1-xCrxS

We employ the full-potential linearized augmented plane wave plus local orbital (FP-L/APW + lo) method based on spin-polarized density functional theory (DFT) in order to investigate the structural, electronic and magnetic properties of ordered dilute ferromagnetic semiconductors Zn_1?xCr_xS and Cd_1?xCr_xS (x = 0.25) in the zinc blende (B3) phase. For the exchange-correlation functional, the generalized gradient approximation GGA (Wu-Cohen 06) has been used. Results of calculated electronic band structures and density of states of these dilute magnetic semiconductors (DMSs) are discussed in terms of the contribution of Cr 3d⁵ 4s¹, Zn 3d¹⁰ 4s², Cd 4d¹⁰ 5s² and S 3s² 3p⁴ partial density of states. For Cr-based systems without n or p-type doping, the stability of the ferromagnetic spin state versus the antiferromagnetic state is predicted. Band structure and density of states studies show half-metallic ferromagnetic nature for both alloys, Zn_1?xCr_xS and Cd_1?xCr_xS. Calculations of the s–d exchange constant N₀α and p–d exchange constant N₀β clearly indicate the magnetic nature of these compounds. From the calculated total magnetic moments we observe that p–d hybridization reduces the local magnetic moment of Cr from its free space charge value and produces small local magnetic moments on the nonmagnetic Zn, Cd and S sites. The robustness of half-metallicity of Zn_1?xCr_xS and Cd_1?xCr_xS as a function of lattice constant is also discussed.