The effect of lattice distortion and orbital mixing on the optical and magnetic properties of cubic RMnO$sub 3$ (R = La, Pr, Nd, Gd, Tb)

TL;DR

This study examines how lattice distortion and orbital mixing influence the optical and magnetic properties of cubic RMnO3 thin films, revealing a correlation between spectral features and magnetic ordering.

Contribution

It provides new insights into the role of lattice distortion and orbital mixing in the optical and magnetic behaviors of RMnO3 compounds.

Findings

Suppression of the 2 eV optical peak with decreasing R-ion size

Spectral weight at 2 eV correlates with A-type antiferromagnetic transition temperature

Orbital mixing and lattice distortion significantly affect optical and magnetic properties

Abstract

We investigated the $ab$-plane absorption spectra of $R$MnO$%_{3}$ ($R$ = La, Pr, Nd, Gd, and Tb) thin films. As the $R$-ion size decreases, we observed a drastic suppression of the 2 eV peak, \textit{i.e.} the inter-site optical transition between spin- and orbital-aligned states across the Mott gap. We found that both lattice distortion and the corresponding orbital mixing of the ordered orbital state should play an important role in the 2 eV peak suppression. We also found that the 2 eV spectral weight is proportional to the $A$-type antiferromagnetic ordering temperature, which suggests that the magnetic interaction might be sensitively coupled to the orbital mixing.