First-principles study of the strain effect with half-metallic ferromagnetism in Cd 1−x V x Te alloys: supercell approaches

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In this work, we study the effect of vanadium (V) dopantson the structural, electronic, and magnetic properties of the CdTe alloys using density functional theory (DFT). The calculations are performed as a function of the concentration of V in the host CdTe semiconductor using a 2 × 2 × 1 tetragonal supercell and a 2 × 2 × 2 cubic supercell. The lattice constants and bulk modulus of Cd 1−x V x Te alloys are determined. The analysis of the density of states shows that the Cd0.75 V0.25Te alloys in both supercells present a total polarization of 100% at the Fermi level, which confirms a stable half-metallic ferromagnetism phase in these materials, in contrast to the Cd 0.9375 V 0.0625 Te and Cd 0.875 V 0.125 Te alloys, which have a polarizability that does not reach 100%. In addition, the electronic band structures are used to estimate the s(p) − d exchange constants mainly resulting from the p − d hybridization between V- 3d and Te-p. Furthermore, the local magnetic moment of V of its free space charge value decreases, leading to the appearance of a small magnetic moment on the Cd and Te sites. Besides, the magnetic stability at different doping concentrations in the ferromagnetic (FM) and anti-ferromagnetic (AFM) states is examined, where the total energy of the systems is considered as a stability criterion. The robustness of the half-metallicity and the curie temperatures under the strain effect are also investigated. Finally, we rely on the binding energy to evaluate the energetic stability of the vanadium in the intrinsic compound CdTe under external deformations.