Magnon relaxation time in ferromagnetic Cr2Ge2Te6 monolayer governed by magnon-phonon interaction

Abstract

Recently, bulk and multi-layer Cr2Ge2Te6 (CGT) has garnered much attention because of its interesting physical properties and promising technological aspects, including information storage and spintronic application. Here, using density functional theory calculations, we investigate the spin-wave spectrum and magnon-phonon interaction (MPI) in the CGT monolayer. The strength of MPI and the magnon relaxation time are estimated by the broadening in the spin-wave spectrum. We find that the MPI in the CGT monolayer exhibits weak in-plane isotropy and a strong wave vector dependence. The broadening of optical magnons is constant near the center of the Brillouin zone, while that for acoustic magnons shows a quadratic wave-vector dependence. Moreover, this wave-vector dependence is independent of temperature. As the temperature increases from 5 K to 55 K, the magnon relaxation time decreases 4 times, revealing the importance of MPI in spin dynamics of the ferromagnetic CGT monolayer. Our work provides an in-depth understanding of the magnon-phonon interaction in the ferromagnetic Cr2Ge2Te6 monolayer.