4d-5p Orbital Mixing and Asymmetric In 4d-O 2p Hybridization in InMnO3: A New Bonding Mechanism for Hexagonal Ferroelectricity

Abstract

Recent studies on the ferroelectricity origin of YMnO3, a prototype of hexagonal manganites (h-RMnO3, where R is a rare-earth-metal element), reveal that the d(0)-ness of a Y3+ ion with an anisotropic Y 4d-O 2p hybridization is the main driving force of ferroelectricity. InMnO3 (IMO) also belongs to the h-RMnO3 family. However, the d(0)-ness-driven ferroelectricity cannot be expected because the trivalent In ion is characterized by a fully filled 4d orbital. Here we propose a new bonding mechanism of the hexagonal ferroelectricity in IMO: intra-atomic 4d(z2)-5p(z) orbital mixing of In followed by asymmetric 4d(z2)(In)-2p(z)(O) covalent bonding along the c axis.