Multi-domain ferromagnetic resonance in magnetic van der waals crystals CrI3 and CrBr3

Abstract Two-dimensional (2D) magnetic van der Waals crystals have received great attentions recently owing to their novel electronic and magnetic properties and rich potentials for low-dimensional and high-density spintronic devices. We investigated the magnetization dynamics of CrI3 and CrBr3 bulk single crystals by utilizing broadband ferromagnetic resonance (FMR) in a frequency range of 1 – 40 GHz and over a wide temperature range of 10 – 300 K. Complex features observed in the FMR spectra are quantitatively described by the multi-domain FMR theory. The minimum resonance frequency fmin in FMR spectra was recognized and analyzed as characteristics of the transition of the domain structure. Micromagnetic simulation on the domain structure and spin dynamics explains that the multi-domain structure exists under strong in-plane magnetic field for CrI3 and CrBr3 and significantly influences the magnetic dynamics properties. Our results also suggest that the linewidths of FMR spectra in CrI3 and CrBr3 are dominated by the magnetic inhomogeneous broadening.