Functionalization of boron phosphide monolayers for spintronic applications by doping with alkali and alkaline earth metals

In this work, new d 0 magnetic materials are developed by doping boron phosphide (BP) monolayers with alkali (Li, Na, and K) and alkaline earth (Be, Mg, and Ca) metals. First-principles calculations confirm the good dynamical and thermal stability of the pristine monolayer. This two-dimensional model is intrinsically a non-magnetic semiconductor with a band gap of 0.90/1.36 eV, as calculated by the PBE/HSE06 functional. B-P chemical bonds are predominantly covalent, generated by electronic hybridization with a small portion of the ionic character formed by the charge transfer from the B atom to the P atom. Doping with Li, Be, and Mg on the B sublattice preserves the non-magnetic nature, causing either a considerable reduction of the band gap or metallization. Meanwhile, the monolayer is significantly magnetized with a total magnetic moment between 0.94 and 3.86 µ B in the remaining cases. Herein, magnetic properties are primarily produced by p orbitals of impurities and their neighboring host atoms, whereas Ca-3 d orbitals also contribute to the magnetism of Ca-doped systems. Moreover, the doping process enables the emergence of either half-metallic or magnetic semiconductors in the BP monolayer to get prospective d 0 magnetic materials and generate spin current. The results presented herein demonstrate the effectiveness of doping with alkali and alkaline earth metals to obtain magnetized BP monolayers with feature-rich electronic properties, such that the doped systems can be recommended for applications in nano spintronic devices.