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We report first-principles investigation on structural, electronic and magnetic properties of 3d transition metal element-doped rock-salt calcium selenide Ca 1 − x TMxSe (TM = V, Cr and Mn) at concentrations x = 0.0625, 0.125 and 0.25. We performed the calculations in the framework of the density functional theory (DFT) using the full-potential linearized augmented plane waves plus local orbitals (FP-LAPW+lo) method within the Wu–Cohen generalized gradient approximation (WC-GGA) for the structural optimization and the Tran–Blaha modified Becke–Johnson (TBmBJ) potential for the electronic and the magnetic properties. The computed spin-polarized band structures and densities of states show that Ca 1 − x CrxSe compounds at all studied concentrations are half-metallic ferromagnets with a complete spin polarization of 100% at Fermi-level while the Ca 1 − x VxSe and Ca 1 − x MnxSe are ferromagnetic semiconductors. The total magnetic moments for Ca 1 − x VxSe, Ca 1 − x CrxSe, and Ca 1 − x MnxSe show the integer values of 3 μ B , 4 μ B , and 5 μ B , respectively, with a major contribution of transition metal elements (TM) in the total magnetization. Also, we reported the calculated exchange constants N 0 α and N 0 β and the band edge spin splitting of the valence (Δ E v ) and conduction (Δ E c ) bands. The ferromagnetism of these compounds is due to the super-exchange and the double-exchange mechanisms in addition to the strong p–d exchange interaction. Therefore, the predicted results indicate that the diluted Ca 1 − x TMxSe (TM = V, Cr, Mn) compounds are suitable candidates for a possible application in the field of spintronic technology. [ABSTRACT FROM AUTHOR]

The structural, electronic and optical properties of the , and are studied by the spin-polarized first-principles calculation. The and are metals in tetragonal structures, while the in trigonal structure is half-metal with 100% spin polarization. The has the biggest static dielectric constant and static refractive index , which may be ascribed to the highest crystal symmetry. The maximum absorption peaks of the , and are located about 44 eV in the ultraviolet region, indicating these materials have good prospect for optoelectronic materials in the ultraviolet range. [ABSTRACT FROM AUTHOR]

The effects of electro-magnetic confining potentials and the s–d exchange interaction between substituted Mn ions and carriers on the spin polarization of carriers in an diluted magnetic semiconductor quantum dot are investigated within the framework of the effective-mass theory. The energy eigenvalues and wavefunctions of a single electron in the presence of an external magnetic field are studied by solving the one particle Schrödinger equation including the conventional Zeeman effect, the s–d exchange interaction and the electric confining potential which describes the dot. The eigenenergy structure for low lying states is strongly dependant on the relative sizes of the s–d exchange interactions and the conventional Zeeman energy splitting. When the spin splitting exceeds the cyclotron energy splitting, the Landau level overlappings occur so that the spin polarization of carriers is induced in low lying energy states. This spin polarization of carriers in the diluted magnetic semiconductor quantum dot can be controlled by changing the electro-magnetic confining potentials. [ABSTRACT FROM AUTHOR]