Doping-Induced Half-Metallic Ferromagnetism in Vanadium and Chromium-Doped Alkali Oxides K<inf>2</inf>O and Rb<inf>2</inf>O: Ab Initio Method

The electronic structures and magnetic properties of K2O and Rb2O alloys doped simultaneously with Cr and V transition elements were investigated using the full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method within the spin-polarized density functional theory (Spin-DFT) and implemented in the WIEN2k package, where the exchange-correlation potential in this approach is described by the generalized gradient approximation with Coulomb repulsion (GGA + U). The substitution of transition metals at 25 % ratio yields the magnetic characteristic of half-metallic ferromagnetism for K2O and Rb2O alloys. The structural properties were estimated in both magnetic and non-magnetic phases, demonstrating the stable ferromagnetic ground phase. The analysis of the electronic structure reveals the excellent half-metallic ferromagnetic nature, with a clear half-metallic gap (EHM) of 0.20 eV for K1.75Cr0.25O alloy. The exploitation of the electronic structure mainly served to determine the spin-polarized exchange-splitting energies Δx(d) and Δx(pd) generated by 3d-TM states, shows that the effective potential of the minority spin is more attractive than that of the majority spin. Moreover, the s−d exchange constant N0α (conduction band) and p−d exchange constant N0β (valence band) describe their contributions during the exchange splitting process. The magnetic properties have indicated that these alloys acquire a magnetic moment when the non-magnetic system is doped with a transition metal (TM). The obtained results from the important magnetic moments of these alloys indicate the potential for their use in spintronic devices.