Raman fingerprint of two terahertz spin wave branches in a two-dimensional honeycomb Ising ferromagnet.

ABSTRACT: Two-dimensional (2D) magnetism has been long sought-after and only very recently realized in atomic crystals of magnetic van der Waals materials. So far, a comprehensive understanding of the magnetic excitations in such 2D magnets remains missing. Here we report polarized micro-Raman spectroscopy studies on a 2D honeycomb ferromagnet CrI₃. We show the definitive evidence of two sets of zero-momentum spin waves at frequencies of 2.28 terahertz (THz) and 3.75 THz, respectively, that are three orders of magnitude higher than those of conventional ferromagnets. By tracking the thickness dependence of both spin waves, we reveal that both are surface spin waves with lifetimes an order of magnitude longer than their temporal periods. Our results of two branches of high-frequency, long-

SUBMITTER: Jin W 

PROVIDER: S-EPMC6269484 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature