Optical Study of the Electronic Structure and Lattice Dynamics of NdBaMn₂O₆ Single Crystals.

ABSTRACT: We investigated the electronic structure and lattice dynamics of double perovskite NdBaMn₂O₆ single crystals through spectroscopic ellipsometry and Raman scattering spectroscopy. The optical absorption band centered at approximately 0.88?eV was assigned to on-site d-d transitions in Mn, whereas the optical feature at approximately 4.10?eV was assigned to charge-transfer transitions between the 2p state of O and 3d state of Mn. Analysis of the temperature dependence of the d-d transition indicated anomalies at 290 and 235?K. The activated phonon mode, which appeared at approximately 440?cm^-1 alongside with the enhancement of the 270?cm^-1 phonon mode, coupled strongly to the metal-insulator transition at 290?K, which was associated with a charge/orbital ordering. Moreover, the MnO₆ octahedral breathing mode at 610?cm^-1 exhibited softening at a temperature lower than 235?K (temperature of the antiferromagnetic phase transition), which revealed the strong coupling between the lattice and magnetic degrees of freedom. The spin-phonon coupling constant obtained was ? = 2.5 cm^-1. These findings highlight the importance of charge-orbital-spin interactions in establishing NdBaMn₂O₆ phases with novel properties.

SUBMITTER: Mero RD 

PROVIDER: S-EPMC6890712 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature