Electric-field-induced fully spin-polarized current in ferromagnetic bipolar Ag, Cr, or Sc-decorated AlN monolayer at room temperature

In this study, we systematically unveil the pivotal role of transition metal adatoms (Ag, Cr, and Sc) in the atomic configuration, electronic structure, and magnetic properties of the aluminum nitride(AlN) monolayer using spin-polarized density functional theory calculations. A pristine AlN monolayer is a direct p-type semiconductor with a non-magnetic nature. Decoration of the AlN monolayer with transition metal atoms induces a transition from non-magnetic to antiferromagnetic states. Bipolarity emerges in the decorated AlN monolayer once the temperature exceeds the magnetic transition temperature. Based on the first-principle calculations, the magnetic transition temperature turns out to be 21, 494.075, and 57.39 K for the AlN monolayers decorated with Ag, Cr, and Sc, respectively. The adatoms’ partially filled valence orbitals hybridizing with the host material is responsible for the ferromagnetic state of each compound. Further investigation demonstrates that stronger chemical adsorption and higher charge transfer are achieved for the Sc-decorated AlN monolayer. The tight bonding of the Sc atom, relative to other adsorbate species, is attributed to the formation of polar covalent bonds between the Sc atom and the nearest N atoms of the AlN monolayer. We further extended our investigation to explore the adsorption properties of decorated AlN monolayers under an external electric field. The energy band gap in all structures begins to decrease as the applied external electric field increases, and half-metallicity occurs when a threshold electric field is reached. These results underscore the significant potential of adatom embellishment of the AlN monolayer for future electronic and spintronic devices.