Electronic structures of hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films

TL;DR

This study explores the electronic structure of hexagonal RMnO3 thin films, revealing specific optical transitions and their dependence on the rare earth ion size, combining optical spectroscopy with first-principles calculations.

Contribution

It provides new insights into the optical properties and electronic transitions of hexagonal RMnO3 thin films, extending previous studies with combined experimental and theoretical approaches.

Findings

Identified two key optical transitions near 1.7 eV and 2.3 eV.

Linked optical peaks to inter-site transitions involving oxygen and Mn orbitals.

Observed systematic shift in optical peak with increasing rare earth ionic radius.

Abstract

We investigated the electronic structure of multiferroic hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films using both optical spectroscopy and first-principles calculations. Using artificially stabilized hexagonal RMnO3, we extended the optical spectroscopic studies on the hexagonal multiferroic manganite system. We observed two optical transitions located near 1.7 eV and 2.3 eV, in addition to the predominant absorption above 5 eV. With the help of first-principles calculations, we attribute the low-lying optical absorption peaks to inter-site transitions from the oxygen states hybridized strongly with different Mn orbital symmetries to the Mn 3d3z2-r2 state. As the ionic radius of the rare earth ion increased, the lowest peak showed a systematic increase in its peak position. We explained this systematic change in terms of a flattening of the MnO5 triangular bipyramid.