Manipulating high Curie temperature of Sm/Ag doped ZnO monolayers by first-principles GGA+U study

This work studies the electronic structure, and magnetic properties of Sm/Ag doped ZnO monolayer by first-principles GGA + U calculations. The results show Sm-doped ZnO monolayer exhibits stable room temperature ferromagnetism with a high magnetic moment of 5.91 μB per unit. The total magnetic moment of the system is mainly contributed by Sm-4f, and the high Curie temperature results from the strong ferromagnetic coupling between the adjacent Sm atoms. The Ag-doped ZnO monolayers undergo magnetic quenching with the Ag doping concentration from 6.25 at.% to 12.5 at.%, which is extremely advantageous for designing and manufacturing magnetic switches. The ZnO monolayer shifts between the non-magnetic to the antiferromagnetic as the distance between neighboring two Ag atoms changes. In Sm-Ag co-doped ZnO monolayer, the Sm atom and Ag atom spin in opposite directions, and the magnetic moments partially cancel out, and the total magnetic moment of the system decreases. In addition, Sm/Ag mono-doped and Sm-Ag co-doped ZnO monolayer exhibited half-metallic behavior due to the impurity energy levels introduced in the bandgap by Sm/Ag dopant, and calculations of the formation energy show that dopants are prone to aggregate. This research may provide a reference for modifying the material properties of ZnO monolayers and designing nano-electronic and spintronic devices.