Tuning the Magnetism by CO Adsorption in Graphene-Like ZnO with Defect

The present work investigates the effect of adsorbate CO molecule on magnetism in the imperfect graphene-like ZnO through first-principles calculations. It is found that the magnetism in an undoped ZnO monolayer with a defect could be effectively tuned just by an adsorbate CO molecule. The graphene-like ZnO with a Zn vacancy shows the ferromagnetism, while a CO molecule is adsorbed on the imperfect graphene-like ZnO monolayer, the charge space redistribution and hybridization result in the ferromagnetism disappearing and the ZnO monolayer becomes nonmagnetic. However, the ZnO monolayer containing an O vacancy transfers from a nonmagnetic state to a magnetic state with 2 mu(B) magnetic moment, when the imperfect ZnO monolayer was adsorbed by a CO molecule. This magnetic change is attributed to the charge transfer between CO molecule and the defect ZnO monolayer. In addition, the ground state for the graphene-like ZnO with two oxygen vacancies adsorbed by two CO molecules with various distance always is the antiferromagnetic (AFM) state. When a CO molecule is reversed, it has no influence on the magnetism of the ZnO monolayer with an O vacancy or a Zn vacancy due to few interactions between the reversed CO and the defect ZnO monolayer. The magnetism for ZnO monolayer could be effectively tuned just by CO adsorption under certain conditions, which is more convenient to tune material magnetism relative to the doping or surface-passivation through molecule decomposition.