Magnetism from 2p states in K-doped ZnO monolayer: A density functional study

Using density-functional–based methods, we have studied 2p-based magnetic moments and magnetic coupling in potassium (K)-doped ZnO monolayer. We find that the substitution of a K atom at a Zn site in a ZnO monolayer induces a magnetic moment of $1.0{\mu }_B$ per cell mainly originating from the O-2p states and has much lower formation energy than a magnetic Zn vacancy. A half-metallic electronic property and long-range ferromagnetic coupling between the magnetic moments are obtained based on the generalized gradient approximation (GGA) calculations, which is explained by a double-exchange–like mechanism. Moreover, with stronger correlation correction on 2p states, the structure of the substitutional K impurity undergoes a Jahn-Teller–like distortion. Incorporating magnetism into a two-dimensional ZnO monolayer will promote its application in nanodevices. (letter)