Spin-Phonon coupling in a candidate 2D atomic crystal magnetic semiconductor

Cr$_{\mathrm{2}}$Ge$_{\mathrm{2}}$Te$_{\mathrm{6}}$ is a particularly interesting material since it is in the very rare class of ferromagnetic semiconductors and possesses a layered, nearly two dimensional structure due to van Der Waals bonds. The van Der Waals bonds make it a candidate two dimensional atomic crystal, which is predicted as a platform to study 2D semiconducting ferromagnets and for single layered spintronics devices. Spin-phonon coupling can be a key factor for the spin relaxation in a spintronics devices. We use polarized temperature dependent Raman scattering to study Cr$_{\mathrm{2}}$Ge$_{\mathrm{2}}$Te$_{\mathrm{6}}$. The spin-phonon coupling has been confirmed in three ways: below T$_{\mathrm{C}}$ we observe a split of two phonon modes due to the breaking of time reversal symmetry; an anomalous hardening of an additional three modes; and dramatic decrease of the phonon lifetimes upon warming into the paramagnetic phase. Our results also suggest the possibility of probing the magneto-elastic coupling using Raman spectroscopy, opening a door for the further study of exfoliated 2D Cr$_{\mathrm{2}}$Ge$_{\mathrm{2}}$Te$_{\mathrm{6}}$. We gratefully acknowledge support from the National Science Foundation (Grant No. DMR-1410846)