Design And Simulation Of Spin Torque Transfer Magnetic Tunnel Junction Structure With T-shape Free Layer

With the rapid rise of information technology and information industry, especially theextension and popularization of multimedia computer network in the world, people’s needfor data storage, processing and transmission showed a geometrically sharp increase, andthus led to the rapid development of information storage technology. Due to itsnon-volatile characteristic, high write endurance, low power consumption, high storagedensity and high read/write speeds, magnetic random access memory causes a wide rangeof interest in the field of storage system, and becomes one of the most possible candidatesin the next generation’s storage system. MRAM application is still in the development andhas much improvement room.This thesis presented a novel STT-MRAM cell with T-shape free layer structure, andmodels were built using micro-magnetic simulation software. The relationship betweenthe switching probability percentage of STT-MRAM cell with T-shape free layer and itsswitching threshold current density has been studied. The performance difference of theT-shape free layer structure and the conventional three-layer structure was compared fromthe aspects of the TMR and the reversal current density, and the reason of the performancedifference is analyzed by modeling the magnetization reversal of the free layer. The heataccumulating effect of the T-shape free layer structure was illustrated by ANSYS finiteelement thermal simulation; the impact of the heat accumulating effect on improving themagnetization reversal efficiency was illustrated from the aspect of perpendicularanisotropy weakening.Then, the T-shape free layer structure was optimized: Firstly, the relationship betweenthe reversal current density of the T-shape cell and the cross-section area of the upper freelayer was studied; then the way to improve the performance of the T-shape cell mostlywithout exceeding the temperature tolerance limitation was presented.Finally, the heat-assisted STT magnetization reversal is studied by micro-magnetic simulation.