Effect Of Interface Engineering On Perpendicular Magnetic Anisotropy In MgO/Fe/Pt

In the process of semiconductor fabrication technology developing to 14nm node,the traditional memory based on polysilicon gradually approaches its limit,the emerging memory is necessary to reform the integrated circuit industry.Spin transfer torque magnetic random access memory?STT-MRAM?has become a research hotspot in the field of microelectronics because of its non-volatility,low power consumption and high density characteristics.It is a critical issue to maintain the thermal stability of the magnetic layer while the device size continues to shrink,which restricts the commercialization of STT-MRAM.Considering the relationship between the thermal stability of the material and its perpendicular magnetic anisotropy?PMA?,it is natural to seek ferromagnetic materials with strong PMA,or to design a new structure of magnetic tunnel junction?MTJ?to improve the PMA.Furthermore,the large critical current density caused by materials with strong PMA is solved by application of electric field.The electric field induced changes in magnetism are limited to the interface atoms for ferromagnetic films.And the interfacial properties will dominate the magnetic anisotropy and directly affect the field induced magnetization reversal at smaller node size.Interface engineering is useful in precisely regulating the magnetic anisotropy of MTJ.In this thesis,the interfacial properties of MgO/Fe/Pt film are studied by first-principle calculations.The electronic structure is discussed based on the second-order perturbation theory.The effects of ferromagnetic layer thickness and heavy metal interlayer on the magnetic anisotropy of MTJ were discussed in detail.On the one hand,the relationship between the magnetic anisotropy of MgO/Fe/Pt interface model and the film thickness of ferromagnetic metal is studied.Unlike other interface models,MgO/Fe₁L/Pt has anomalous in-plane magnetic anisotropy because of the dominant density of states of the Fe atom dx²-y² orbital component at fermi level.In addition,it has much higher magnetoelectric coefficient due to the strong interaction between the interfaces.The oscillating behavior between magnetic anisotropy and ferromagnetic film thickness can be attributed to the coupling between the interfaces,as well as the relative position change of interface configuration.On the other hand,in order to enhance the PMA,the effects of heavy metal interlayer on the magnetic anisotropy of MTJ were elucidated.Based on first-principle calculations,the magnetic anisotropy energies of interface models with different heavy metal materials were obtained.It is found that the Rh monoatomic layer has great impact on the PMA by analyzing the electronic structure.Then,the influence of interlayer position on the magnetic anisotropy behavior is considered.The results suggest that different interlayer position will lead to great difference in MAE,and the MgO/Fe interface is the best choice.Finally,through the calculation of the thickness gradient model,it is demonstrated that the PMA of the interface model can be improved by inserting Rh film within a certain thickness range.