Study of electronic and magnetic properties of Mn-doped KNbO3: A first-principles approach

Changes in the electronic structure of Mn-doped KNbO3 have been studied by first-principles calculations, using the projector-augmented-wave method, within the generalized gradient approximation with on-site Hubbard-U potential (GGA + U), for the exchange-correlation potential. In our study, we analyze different Mn-dopant concentrations, namely 2.5, 5, and 10 %, with Mn entering Nb, K or both sites. Our results show that all doped structures acquire a ferromagnetic character. When Mn enters in Nb or K sites, the structures acquire a metallic character and when Mn enters in both Nb and K, the structures conserve a semiconductor character. The site-decomposed partial density of states shows that the metallic character comes from an up-shift in energy of O-p orbitals when Mn enters Nb sites and a down-shift energy when Mn enters K sites. Furthermore, when Mn enters in both Nb and K sites, a combination of the former cases takes place, resulting a structure with a semiconductor character. Analyzing the formal oxidation states of component atoms allows us to explain changes in electrical and magnetic properties.