It is well known that the Gilbert relaxation time of a magnetic moment scales inversely with the magnitude of the externally applied field, H, and the Gilbert damping, α. Therefore, in ultrashort optical pulses, where H can temporarily be large, the Gilbert relaxation time can momentarily be extremely short, reaching even picosecond timescales. Here we show that for typical ultrashort pulses, the magnetization can respond within the optical cycle such that the optical control of the magnetization emerges by merely considering the optical magnetic field in the Landau-Lifshitz-Gilbert (LLG) equation. Interestingly, when circularly polarized optical pulses are introduced to the LLG equation, an optically induced helicity-dependent torque results. We find that the strength of the interaction is determined by N = ayH/F"#, where fc!"# and yare the optical frequency and gyromagnetic ratio. Our results illustrate the generality of the LLG equation to the optical limit and the pivotal role of the Gilbert damping in the general interaction between optical magnetic fields and spins in solids.
|Original language||American English|
|Title of host publication||Spintronics XVI|
|Editors||Jean-Eric Wegrowe, Joseph S. Friedman, Manijeh Razeghi|
|State||Published - 2023|
|Event||Spintronics XVI 2023 - San Diego, United States|
Duration: 20 Aug 2023 → 24 Aug 2023
|Name||Proceedings of SPIE - The International Society for Optical Engineering|
|Conference||Spintronics XVI 2023|
|Period||20/08/23 → 24/08/23|
Bibliographical notePublisher Copyright:
© 2023 SPIE.
- all-optical magnetization switching
- helicity dependent magnetization switching
- Landau-Lifshitz-Gilbert equation
- ultrafast magnetization dynamics