Magnetic fluctuation effects on Raman scattering in the organic superconductor κ-ET2Cu[N(CN)2]Br

We present a study of the 503, 880, 890, 901, 920, and 1475 cm−1 Raman active κ-ET2Cu[N(CN)2]Br single crystal phonons, around T=40 K, where an anomaly in the longitudinal sound velocity and antiferromagnetic spin fluctuations have been detected. Doublets, narrowing of phonon lines and non-monotonic intensity variations, as a function of temperature, are observed indicating a possible interaction between phonon and correlated electrons.