Spin-phonon coupling in melanothallite Cu2OCl2

Since interesting magnetodielectric properties were discovered in terbium-based manganites, the search for new magnetodielectric multiferroic materials with high Curie temperatures and strong magnetodielectric coupling has been intense. Recently, it was reported that synthetic melanothalllite, the oxahalide Cu2OCl2, is a spin-driven multiferroic magnetodielectric with Néel temperature around 70 K, which is an exceptionally high critical temperature compared to other spin-driven ferroelectric materials. In this letter, we have probed the spin-phonon coupling in Cu2OCl2 by Raman spectroscopy, showing that the incommensurate magnetic structure induces a spin-phonon coupling in accord with the mean field theory and similar to the one observed in several stretching modes of perovskite compounds.