Strain effects on the magnon-magnon interaction and magnon relaxation time in ferromagnetic ${\mathrm{Cr}\mathrm{Ge}\mathrm{Te}}_3$

In the synthesis of two-dimensional (2D) materials and the fabrication of 2D devices, the strain introduced by lattice mismatch is inevitable. Meanwhile, strain is also a frequently used strategy to improve the Curie temperature of 2D magnets. However, the impact of strain on the magnon relaxation time is unclear. In this work, we investigated the impacts of strain on the magnon-magnon interaction and magnon relaxation time in the ferromagnetic ${\mathrm{Cr}\mathrm{Ge}\mathrm{Te}}_3$ monolayer by combining first-principles calculations and theoretical analysis. We find the magnon relaxation times in strained and unstrained ${\mathrm{Cr}\mathrm{Ge}\mathrm{Te}}_3$ monolayers have similar dependences on temperature, wave vectors, and magnetic fields. However, the magnon relaxation time is remarkably reduced by tensile strain. When the external magnetic field is 0.1 T, the maximum shortened ratio of the magnon relaxation time can reach 49.3%, revealing an enhancement of the magnon-magnon interaction. With the magnetic field strengthening, the shortened ratio of the magnon relaxation time decreases, but it still reaches up to 19.4% under a 5-T magnetic field. This shortening of magnon relaxation time is undesired for applications in spintronics. Our work provides physical insights into the impacts of strain on 2D magnets.