Research On The Electrical Characteristics Of New Nano-storage Devices

Magnetic tunnel junction（MTJ）has a wide range of applications in the field of magnetic random access memory（MRAM）due to its excellent energy properties.We use the method of combining the first principles of density functional theory and the LLG equation,use FLEUR software to calculate and analyze the electronic structure of Bi₂Se₃ and Bi₂Te₃;use OOMMF software to analyze the dynamics of spin transfer moment magnetic random access memory（STT-MRAM）The characteristics were simulated and calculated.Finally,a spin-orbit torque magnetic random access memory（SOT-MRAM）model combining topological insulators and ferromagnetic materials is proposed,and its dynamic characteristics are simulated.The main work content includes the following aspects:（1）Based on DFT first-principles theory and NEGF theory,this paper calculates the unit cell parameters,energy band structure and density of states distribution of Bi₂Se₃ and Bi₂Te₃ through FLEUR software,and analyzes these two materials.The calculation results show that the p-orbital states of Se,Te and Bi atoms in Bi₂Se₃ and Bi₂Te₃ construct their conduction band and valence band,and the minimum conduction band and maximum valence band are located at the high symmetry point of the same Brillouin zone Point G is a direct band gap structure.It can be concluded that Bi₂Se₃ and Bi₂Te₃ are both topological insulator structures,which can replace the heavy metal layer as the conductive layer of SOT-MRAM.（2）Based on the LLG equation,this paper uses the OOMMF software to simulate the magnetic random access memory based on the STT effect,and calculates the flipping of the vertical magnetic moment component under different STT currents.It is concluded that under different STT currents,the magnetic moment of the free layer exhibits three changes:gradual attenuation,stable amplitude,and magnetic moment reversal.And the smaller the thickness of the free layer,the shorter the time required to realize the magnetic moment reversal,and the faster the operating speed of the memory.（3）This paper proposes a new type of ferromagnetic/topological insulator structure based on SOT effect magnetic random access memory.The SOT-MRAM uses the topological material Bi₂Se₃instead of ordinary heavy metal materials as the conductive layer,which destroys the symmetry of the structure,so that its storage properties can be achieved without an external magnetic field.We calculated the flipping of the vertical magnetic moment component under different SOT currents and different damping constants.It is calculated that after the vertical magnetic moment component flips and the magnetization distribution diagram,it can be seen that the critical current of the SOT-MRAM structure is smaller than that of the STT-MRAM,and it has a good energy effect.