Influences of interfacial terminations on electronic structure and magnetoelectric coupling in Fe/KNbO3 superlattices

We study the electronic structures and the magnetoelectric (ME) effect in Fe/KNbO3 superlattices theoretically. The interior KNbO3 layers in superlattices with the NbO2 terminations are insulating. While they are metallic for the KO terminations. The interface FeNb and FeO bonds induce large magnetic moments on Nb and O atoms. The magnitude of the induced magnetic moments is related to the polarization direction of the KNbO3 layers. We obtain a large ME effect in NbO2-terminated superlattices. However the ME effect is negligible in KO-terminated superlattices due to the opposite sign of variations of magnetic moments on O and Fe at two interfaces.