Microscopic Three-temperature Model For All-optical Switching In GdFeCo

The development of magnetic data storage is an exciting field of fundamental research and the most important application for magnetic materials.Commonly,the methods for magnetic recording are external magnetic field,heat-assisted and all-optical switching(AOS).However,compared with the aforementioned two methods,all-optical switching can complete the switching process within 100 ps,which has a distinct advantage in the speed of storage.Therefore it has attracted extensive attention from researchers.The atomic spin model and the Landau-Lifshitz-Bloch(LLB)model only use the damping parameters to phenomenologically describe the transfers process of angular momentum,so the quantized information of angular momentum transfer during magnetic inversion cannot be given.Since the quantum transfer process of angular momentum is an important basis for explaining the microscopic mechanism of AOS,how to obtain the quantized information of angular momentum transfer is the key to correctly understand AOS of magneto-optical materials.In 2009,based on the Elliott-Yafet spin scattering theory,B.Koopmans et al.established a microscopic three-temperature model that clearly shows the quantized angular momentum transfer process between electrons,lattices and spins.Corresponding to the atomic spin model and the LLB model that introduce the effective thermal field,if the effective thermal field is introduced into M3 TM,the AOS process of Gd Fe Co can be calculated and simulated.And the angular momentum transfer quantized information of the electrons,lattices and spins in this process can be obtained.Firstly,the all optical switching process caused by the inverse Faraday effect of Co/Pt material is repeated to verify the correctness of M3 TM in this paper.The effects of different polarizations on the inversion are simulated respectively: right-handed polarized light and linearly polarized light cannot make materials reverse however left-handed polarized light can.Then we repeated the effect of pulse fluences and pulse widths on materials.Finally,we repeat the two-dimensional strength plan of Co/Pt material Through verification,it was found that M3 TM can correctly reflect theall-optical inversion process caused by the inverse Faraday effect.In order to investigate the all-optical reversal by thermal effects,this paper introduces the effective thermal field into M3 TM.The AOS dynamics and the final magnetization states of Gd Fe Co induced by single laser pulses with different energy doses and pulse widths are calculated and analyzed concretely.Through theoretical simulation combined with the corresponding experimental verification,we found that as the laser energy density increases the magnetization will change from no switching to switching to demagnetization.The pulse width of the laser will also affect the magnetization.As the width increases,the reversal window of the magnetic material gradually increases.In addition,utilizing the bump and probe experiment,we observed the magnetization revolution at different times during the magnetic material reversal process.We observed the nonequilibrium phenomenon of the material firstly and switching area reduces gradually until appearance of switching phenomenon.M3 TM provides a more concise time-varying expression of the magnetization of Gd Fe Co and explicitly addresses the dissipation of angular momentum after the laser-pulse excitation,which enables faster calculations of the heat-induced magnetization dynamics in magneto-optical materials with large areas.