First principle study on the electronic and magnetic properties in Zn _0.75Cr _0.25M (M = S, Se, Te) semiconductors

Using the first-principle method, the structural, electronic and magnetic properties of Zn _0.75Cr _0.25M (M = S, Se, Te) have been investigated. The calculated formation energy and cohesive energy of Zn _0.75Cr _0.25M are negative and the absolute values of them decrease with the increase of atomic radius as well as the electronegativity of the anions. Zn _0.75Cr _0.25M display half-metallic characteristics with energy band gaps of 1.06, 0.65 and 0.83 eV, respectively. The conventional gaps for minority spin are 2.91, 2.16 and 1.75 eV for Zn _0.75Cr _0.25S, Zn _0.75Cr _0.25Se and Zn _0.75Cr _0.25Te respectively, which decrease with the increase of anion radius successively, similar to that observed in the binary compounds of ZnM. For all the three materials, exchange splitting energies ^Δx(pd) due to the effect of Cr 3d state are negative, implying that the effective potential is more attractive for minority spin than that for majority spin, and the absolute value of ^Δx(pd) decreases with the increase of atomic radius of anions. The calculated positive values of ^N0α suggest interactions between Zn-s and Cr-3d states are repulsive, while the negative values of ^N0β show that p-d interactions at the valence band are more attractive. All these conclusions demonstrate that Zn _0.75Cr _0.25M are promising candidates for practical applications in spintronics.