Research About Current-Induced Field Free Magnetization Switching In Single Layer L10FePt Based On Spin-Orbital Torque

In the research of magnetic storage devices,the L1₀-FePt has shown excellent potential as a magnetic storage device in experiments.The L1₀-FePt single-layer film has extremely high vertical magnetic anisotropy,and the coercivity can reach up to 7 T depending on the growth conditions.The high coercivity and vertical magnetic anisotropy bring high stability and strong anti-interference to the device,which can meet the demand for storage unit miniaturization to 3 nm and achieve an ultra-high storage density of 10 Tb/inch.Recent studies have found that the spin-orbit torque effect in L1₀-FePt single-layer films can drive the magnetic moment to flip,providing a new pathway for efficient manipulation of the L1₀-FePt magnetic moment.However,to achieve the directed flip of the vertical magnetic moment driven by the spin-orbit torque effect,an in-plane bias magnetic field or a similar acting field needs to be applied.The introduction of on-chip magnetic fields not only complicates the device but also greatly affects power consumption and integration.To make FePt devices viable for industry,one of the key challenges is to achieve magnetic switching of L1₀-FePt through current-driven manipulation without an external magnetic field（fully electrical control）.According to the literature survey,this goal has not yet been achieved.Therefore,this thesis focuses on this problem and proposes a new strategy:achieving free field magnetic moment switching of L1₀-phase FePt by growing the film on a vicinal substrate which induced the additional stress to break the symmetry of the film.In this thesis,L1₀-phase FePt is prepared by co-sputtering.We investigated the dependence of the thin film lattice structure and magnetism on different vicinal substrates.Characterized the magnetic poperties of L1₀-phase FePt through SQUID.And testified high-ordered experimental samples can be effectively obtained under these experimental conditions.Investigating the current-driven magnetization reversal characteristics of L1₀-FePt samples,systematically.We observed effective field-free current-driven magnetization switching in devices which grown on vicinal substrate,and proved the decisive influence of the vicinal substrate on field-free switching.This thesis also studied the dependence of magnetic switching on different substrates,and discoverd that there is great control space by introducing the tilted substrate.Furthermore,this thesis used anisotropic magnetoresistance experiments to verify the direct cause of magnetic switching is the tilting of the sample magnetic moment.Based on the simulation results of tilted magnetic moment samples,it has been proven that the reason for the free field switching of L1₀ phase FePt is the tilting of FePt magnetic moment caused by the vicinal substrate.Simultaneously using harmonic testing to characterize the effective field efficiencyβ_L（T）of the sample after introducing the substrate,combined with literature research and inference,leads toβ_L（T）andαThe possible reason for the absence of dependency is that the vicinal substrate introduces stress in different directions.This thesis demonstrates that vicinal substrates can induce effective field-free magnetic switching in L1₀-FePt thin films without requiring additional functional layers or asymmetric designs.This approach is simple and efficient and suitable for industrial wafer-level device growth,providing new theoretical and experimental evidence for the use of L1₀-FePt as MRAM devices in the future.