Abstract
We report polarized Raman results of magnetic superconductor to explore crystal-field (CF) excitations and spin-phonon interactions. In addition to the phonon mode at , we observed additional Raman modes at 124, 151, and . By careful analysis of the temperature evolution of these modes, we attribute the excitation to a CF transition. The 151 and modes correspond to zone-folded phonons because they are completely quenched for . With increasing temperature across , the excitation diminishes rapidly in intensity and, interestingly, an additional mode appears at . This excitation grows in intensity with increasing temperature toward 50 K and gradually decreases with increasing temperature further. We attribute the excitation to an excited CF transition from a low-lying CF level at to the higher CF level at . Anomalous temperature-dependent behavior of the phonon mode was observed in peak energy and in spectral width, i.e., both the phonon energy and the linewidth are enhanced in the vicinity of , suggesting the presence of strong spin-phonon interactions near the antiferromagnetic ordering temperature in .
- Received 24 June 2010
DOI:https://doi.org/10.1103/PhysRevB.82.064423
©2010 American Physical Society