Temperature-dependent and anisotropic optical response of layered Pr${}_{0.5}$Ca${}_{1.5}$MnO${}_4$ probed by spectroscopic ellipsometry

Abstract

We study the temperature dependence as well as anisotropy of optical conductivity (${\sigma }_1$) in the pseudocubic single crystal Pr${}_{0.5}$Ca${}_{1.5}$MnO${}_4$ using spectrocopic ellipsometry. Three transition temperatures are observed and can be linked to charge-orbital ($T_{CO/OO}$ $\sim$ 320 K), two-dimensional-antiferromagnetic (2D-AFM) ($\sim$ 200 K), and three-dimensional AFM ($T_{\mathrm{N}}\sim$ 125 K) orderings. Below $T_{CO/OO}$, ${\sigma }_1$ shows a charge ordering peak ($\sim$0.8 eV) with a significant blue shift as the temperature decreases. Calculations based on a model that incorporates a static Jahn-Teller distortion and assumes the existence of a local charge imbalance between two different sublattices support this assignment and explain the blue shift. This view is further supported by the partial spectral weight analysis showing the onset of optical anisotropy at $T_{CO/OO}$ in the charge-ordering region ($0.5-2.5$ eV). Interestingly, in the charge-transfer region ($2.5-4$ eV), the spectral weight shows anomalies around the $T_{2D-\mathrm{AFM}}$ that we attribute to the role of oxygen-$p$ orbitals in stabilizing the CE-type magnetic ordering. Our result shows the importance of spin, charge, and lattice degrees of freedom in this layered manganite.

6 pages, 3 figures

References in corpus (4)

• Variation of charge/orbital ordering in layered manganites Pr1-xCa1+xMnO4 investigated by transmission electron microscopy
• First order phase transition in the frustrated triangular antiferromagnet CsNiCl3
• Effect of antiferromagnetic spin correlations on lattice distortion and charge ordering in Pr${}_{0.5}$Ca${}_{1.5}$MnO${}_4$
• Coexistence of long-ranged charge and orbital order and spin-glass state in single-layered manganites with weak quenched disorder

Cited by in corpus (1)

• Theoretical study of optical conductivity of graphene with magnetic and nonmagnetic adatoms