Spectral sensitive phonon wipeout due to a fluctuating spin state in a Fe2+ coordination polymer
Abstract
Raman scattering in the spin-crossover system [Fe(pmd)(H2O)Au(CN)22]*H2O reveals a complex three-phase spin-state transition in contrast to earlier observations in magnetization measurements. We observe different spin state phases as function of temperature and electromagnetic radiation in the visible spectral range. There exists a fluctuating spin state phase with an unexpected wipeout of the low frequency phonon scattering intensity. Furthermore we observe one phase with reduced symmetry that is attributed to a cooperative Jahn-Teller effect. Pronounced electron-phonon interaction manifests itself as a strong Fano-resonance of phonons related to FeN6 and FeN4O2 coordination octahedra. Density functional theory supports this interpretation.