Asymmetric Ho 5d-O 2p hybridization as the origin of hexagonal ferroelectricity in multiferroic HoMnO(3)

Abstract

HoMnO3 (HMO) is one of the most extensively studied hexagonal manganites owing to its strong tendency of the magnetoelectric coupling. In spite of extensive studies on its multiferroic properties, however, little progress has been made in our understanding on the electronic origin of the hexagonal ferroelectricity in HMO. Considering this, we have examined the bonding mechanism that gives rise to an off-centering ferroelectric distortion along the c axis of the hexagonal P6(3)cm unit cell by exploiting density-functional theory calculations. We have shown that the asymmetric 5d(z2)(Ho)-2p(z)(O-A) hybridization is primarily responsible for the manifestation of this structural ferroelectricity in HMO.