Theoretical Study On The Effect Of Temperature In The Magnetic Tunnel Junctions With Single Crystal 2D-Material Barrier

In the field of spintronics,magnetic tunneling junctions have become the subject of intense study as they possess great potential to be basic unit of the next generation of magnetic random access memory(MRAM).The barrier of conventional magnetic tunnel junctions are usually prepared by oxides such as Al₂O₃ and Mg O.However,the complicated process for preparing the magnetic tunnel junctions with oxide barrier leads to higher cost.Single crystal 2D-material provides a new approach to prepare low cost magnetic tunnel junctions due to the characteristics of simple preparation.Therefore,magnetic tunnel junctions with single crystal 2D-material barrier have been widely studied in recent years.It is found from the experiment that the TMR changes non-monotonically with temperature which is different from the conventional magnetic tunnel junctions with Mg O.Such temperature effect needs to be explained theoretically.In order to solve this problem,this paper develops a tunneling theory based on the optical method and metal-barrier-metal tunneling theory for magnetic tunnel junctions with single 2D-material crystal barrier.Using the above model,the temperature effects of magnetic tunnel junctions with graphite barrier and MoS₂ barrier are studied.The main research results are as follows:1.For the case of ordinary ferromagnetic electrodes,the tunneling resistance R_P,R_AP and TMR of magnetic tunnel junctions with graphite barrier and MoS₂ barrier oscillate with temperature.The physical mechanism comes from the interference effect between the component waves after the electron is scattered by the periodic barrier.In addition,this paper also studies the effect of lattice distortion on the temperature effect of magnetic tunnel junctions with single 2D-material crystal barrier.The results show that the R_P,R_AP and TMR are more sensitive to temperature when strain and defect concentration increase.On the contrary,the R_P,R_AP and TMR are less sensitive to temperature when recovery temperature increase.The reason is that the barrier periodic potential is more sensitive to temperature when strain and defect concentration increase,and less sensitive to temperature when recovery temperature increase.2.This paper studies the effect of ordinary ferromagnetic electrode parameters on the temperature characteristics of magnetic tunnel junctions with graphite barrier and MoS₂ barrier.The results show that the R_P of magnetic tunnel junction with graphite barrier decreases with the chemical potential?and the half splitting energy?of the ferromagnetic electrode,and the R_AP and TMR decrease with?and increase with?.The R_P of magnetic tunnel junction with MoS₂ barrier increase with?and?,the R_AP and TMR decrease with?,and increase with?.The reason is that different?and?will make the band density of states near the Fermi surface change,and then affect the tunneling current.3.This paper studies the thickness effect magnetic tunnel junctions with graphite barrier and MoS₂ barrier with different temperature under the condition of ordinary ferromagnetic electrode.The results show that the oscillation period and amplitude of the R_P,R_AP and TMR decrease with the increasing temperature.In addition,this paper also studies the effects of strain,defect concentration and recovery temperature on the thickness characteristics of two kinds of magnetic tunnel junctions.The results show that the oscillation periods and amplitudes of the R_P,R_AP and TMR increase when the strain increases.However,the oscillation periods and amplitudes of the R_P,R_AP and TMR are almost unchanged when the defect concentration and recovery temperature increase.The reason is that comparing with the defect concentration and recovery temperature,the periodic potential of the barrier layer is sensitive to strain.4.For the case of half-metallic ferromagnetic electrodes,the R_P of magnetic tunnel junctions with graphite barrier and MoS₂ barrier oscillate with temperature,and the R_AP decrease monotonously with temperature.The results are different from those of ordinary ferromagnetic electrodes.It is because of the half-splitting energy?is larger than the chemical potential?in the case of half-metallic ferromagnetic electrodes,and then makes the p_–and p_-components of the anti-parallel channel decay.Therefore,the coherence between the components no longer causes the oscillation of the tunneling resistance.In addition,the tunneling periodic potential increasing with temperature make the partitioning transition obtain higher energy,and then make the electrons that contributing to the anti-parallel tunneling conductance increase.So the R_AP is smaller.