Simulation And Research On All-optical Magnetic Switching Of L1₀-FePt Nano-paricles

Since Fritz Pfleumer invented the first magnetic tape recorder in 1928,more and more researchers have been engaged in the research of magnetic recording technology,which has led to the rapid development of magnetic recording technology and laid a solid foundation for the rapid and stable development of Internet technology.In the current era of data,there is an urgent need to develop new magnetic recording technology to meet the storage needs,among which all-optical magnetic recording techonology has attracted great attention.L1₀-FePt nano-particles are suitable for all-optical switching magnetic recording media because of its high anistropy.Howerver,the mechanism of its all-optical magnetization switching is still unclear,and the further research has long-term practical significance.In this thesis,an atomistic simulation model of L1₀-FePt nano-particles based on the general atomistic simulation model is used.The Cuire temperature is calculated by monte carlo method,and the time-dependent electron temperature and magnetization caused by linearly polarized laser pulse are calculated respectively by two temperature model and Heun method.The above results are consistent with the existing experimental results,which verify the rationality of atomistic simulation model and physical parameters used.A possible mechanism on the all-optical magnetic switching of L1₀-FePt nano-particles induced by circularly polarized laser pulse is proposed,which is caused by the combination effect of inverse Faraday effect and magnetic circular dichroism.The final net magnetization of L1₀-FePt particle film after multiple circularly polarized laser pulses is calculated by a simple accumulative model.When the optical magnetic field is-0.1T and the magnetic circular dichroism ratio is 2%,the final net magnetization is 10%-20%of saturation magnetization,whose direction only depends on the polarization of laser pulse.Meanwhile a modest external magnetic field can offset the all-optical switching.The two results are in agreement with the experimental results of Lambert et al.When the optical magnetic field is-0.4T,absolute switching can be achieved.