Abstract
We theoretically study the mechanism of the all-optical magnetic switching by combining the Rashba effect and stimulated Raman scattering. In hydrogenlike systems, we show that the Rashba effect splits the energy band and stimulated Raman scattering transits the electrons between the lambda three-level system and controls the spin states to reverse the orientation of magnetization. The dynamics of electrons are described with the Lindblad equation in a few hundreds of femtoseconds. We further investigate the influence of laser intensity and wavelength on the probability of spin-flip in a ferromagnetic material, CoPt.
Highlights
It has been reported that circularly polarized femtosecond laser pulses can deterministically switch the orientations of magnetization of certain materials [1,2,3,4,5], including rare-earth transition metal alloys [3,6], CoPt [7,8,9], and their multilayer films [10]
Spin-up may transform to spin-down, and all the oscillation will be described in the Rabi model [33,34,35]
In consideration of the result of Qaiumzadeh et al [31], the laser-induced Rashba effect is treated as an effective magnetic field
Summary
It has been reported that circularly polarized femtosecond laser pulses can deterministically switch the orientations of magnetization of certain materials [1,2,3,4,5], including rare-earth transition metal alloys [3,6], CoPt [7,8,9], and their multilayer films [10]. The derived effective Hamiltonian and standard magnetic field by Pershan, M(t) ∝ E(t) ∗ E∗(t) , is not applicable for sub-picosecond and high-intensity laser scenarios, because the research assumed that the variation of the pulse amplitude is negligible during the magnetization switching process. SRS stimulates the electron transition and changes the spin state, which is helicity dependent, in magnetic materials. The circularly polarized laser-induced Rashba effect produces an effective magnetic field on CoPt [31]. The laser drives electrons to oscillate between the two sub-bands and virtual excited state, and all of the three constitute a Λ three-level system In these transitions, spin-up may transform to spin-down, and all the oscillation will be described in the Rabi model [33,34,35]. The final probability of spin state is controllable with the intensity and wavelength of laser
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