Abstract
The magnetization orientation dependence of Gilbert damping and ultrafast demagnetization were investigated in single-crystalline films grown on a MgO(100) substrate by the time-resolved magneto-optical Kerr effect technique. The intrinsic Gilbert damping coefficient extracted from the time evolution of magnetization precessions shows a remarkably large anisotropy with a ratio of more than 300% for magnetization orientations along the and axes. Such a large anisotropy of Gilbert damping persists to high frequencies up to , where the effect of two-magnon scattering is suppressed. In contrast to the anisotropic Gilbert damping, the ultrafast demagnetization time and ratio for different in-plane magnetization orientations are nearly isotropic with the magnetization orientation. Although anisotropic Gilbert damping can be explained by the variation of spin-orbit coupling with the magnetization orientations, our results demonstrate that the role of spin-orbit coupling in the high nonequilibrium state after ultrafast laser excitation is isotropic in driving ultrafast spin-flip processes.
- Received 22 February 2021
- Revised 5 June 2021
- Accepted 24 June 2021
DOI:https://doi.org/10.1103/PhysRevB.104.024404
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