Searching for d⁰ spintronic materials: bismuthene monolayer doped with IVA-group atoms

Doping with non-metal atoms may endow two-dimensional (2D) materials with feature-rich electronic and magnetic properties to be applied in spintronic devices. In this work, the effects of IVA-group (C, Si, and Ge) atom doping on the structural, electronic and magnetic properties of bismuthene monolayer are investigated by means of first-principles calculations. Pristine monolayer is a direct gap semiconductor with band gap of 0.56 eV, exhibiting Rashba splitting caused by spin-orbit coupling. Regardless doping level, C and Si incorporation leads to the emergence of significant magnetism, which is generated mainly by the dopants as demonstrated by the spin density illustration. Depending on the dopant nature and concentration, either half-metallic or magnetic semiconductor characters can be induced by doping, which are suitable to generate spin current in spintronic devices. Further study indicates an energetically favorable antiferromagnetic coupling in the C- and Si-doped systems, suggesting the predominant Pauli repulsion over Coulomb repulsion. Meanwhile, bismuthene monolayer is metallized by doping Ge atoms. Magnetization occurs with 12.5% and 5.56% of Ge atoms, meanwhile the non-magnetic nature is preserved under lower doping level of 3.125%. Results presented herein may introduce C and Si doping as efficient approach to functionalize non-magnetic bismuthene monolayer, enriching the family of 2D d⁰ magnetic materials for spintronic applications.