Density functional theory investigation of half-metallic ferromagnetism in V-doped GaP alloys

Abstract

The spin polarized structural, electronic, and magnetic properties of zincblende Ga1−xVxP (x = 0, 0.25, 0.50, 0.75, and 1) alloys are studied by using the full-potential linearized augmented plane waves with local orbital (FP-L/APW + lo) method within the spin-polarized density functional theory (spin-DFT). The exchange and correlation (XC) energy is defined in all this approach by the generalized gradient approximation (GGA-PBE) of Perdew-Burke-Ernzerhof, whereas the GGA + U (U is the Hubbard term of the Coulomb repulsion correlation) functional is employed specially to treat and improve the electronic and magnetic properties of these compounds. The structural properties show the stability of Ga1−xVxP alloys in ferromagnetic phase, where their equilibrium structural parameters (lattice constant (a0), bulk modulus (B0), and its first-pressure derivative (B’) are evaluated. The elastic constants for the cubic system (C11, C12, and C44) and anisotropy are computed in the goal to prove the mechanical stability of these compounds. The electronic results reveal that both Ga0.25V0.75P and VP alloys have a perfect half-metallic nature, while the Ga0.75V0.25P alloy is a semiconductor. From band structures, we observe that the unfilled 3d-V orbitals increase the rise of spin-exchange splitting energy Δx(d) and Δx(pd); consequently, we found that the minority-spin case presents an attractive effective potential comparing to the majority-spin case. The total magnetic moment of Ga0.75V0.25P, Ga0.25V0.75P and VP alloys are found in integer value (2μB), affirming their complete half-metallic behavior. Moreover, we estimate the s-d exchange constant N0α (conduction band) and the p-d exchange constant N0β (valence band) to analyze contributions of conduction and valence bands in the exchange splitting process; in the other hand, the observed p-d hybridization reduces the atomic magnetic moment of V element from its free space charge value and produces weak local magnetic moments on the nonmagnetic sites of Ga and P atoms.