Theoretical Study On The Magneto-Seebeck Effect Of Magnetic Tunnel Junctions With A Single-Crystal Barrier

Magnetic tunnel junctions(MTJs),a spintronic device with high resistance and high integration,have been widely used in information storage and other fields.However,in practical applications,these characteristics make magnetic tunnel junctions prone to "waste heat",which affects device performance.In spin-thermoelectronics,"waste heat" can be reused through spin,charge,entropy and energy transfer to develop "green" information and communication technologies.Therefore,the Tunnel Magneto-Seebeck(TMS)effect in magnetic tunneling junctions has been attracting attention.In particular,the Tunnel Magneto-Seebeck effect in Mg O-based magnetic tunnel junctions has been extensively studied,and the essential difference between Mg O-based magnetic tunnel junctions and conventional Al-O-based magnetic tunnel junctions is that their potential layers are made of singlecrystal thin films,and the periodicity of single-crystal potential layers has a significant effect on the Tunnel Magneto-Seebeck effect in magnetic tunnel junctions.Theoretically,this effect needs to be investigated.On the other hand,experimentally,different heating methods yield Seebeck coefficients with significant size differences: the intrinsic Seebeck coefficients obtained by direct Joule heating methods are two to three orders of magnitude smaller than those obtained by other methods.This is because other methods cause additional effects.Therefore,a theoretical model consistent with the experimental results of the intrinsic Seebeck coefficients needs to be constructed.Based on the above two reasons,a theoretical model of single-crystal potential layer magnetic tunneling junctions based on the optical diffraction method is constructed in this paper,and the Tunnel Magneto-Seebeck effect of single-crystal potential layer magnetic tunneling junctions is investigated using this theoretical model.The main results of the study are as follows:1.In this thesis,the effects of the ferromagnetic electrode of a magnetic tunneling junction on the Tunnel Magneto-Seebeck effect of the magnetic tunneling junction of a single crystal potential barrier layer in the case of a normal metallic ferromagnetic electrode is investigated,focusing on the effect on the Seebeck coefficient and the TMS thickness effect.The results show that the periodicity of the single-crystal potential barrier layer causes the strong coherence of the tunneling electron wave,which in turn leads to the oscillation of the Seebeck coefficient with the thickness of the potential barrier layer,the chemical potential of the ferromagnetic electrode and the semi-exchange cleavage energy of the ferromagnetic electrode.In addition,the amplitude of Seebeck coefficient oscillation with the barrier thickness increases monotonically with the half-exchange cleavage energy and decreases monotonically with the chemical potential;the period of Seebeck coefficient oscillation with the chemical potential and half-exchange cleavage energy decreases monotonically with the barrier thickness.Since the Seebeck coefficient has an oscillatory effect,there may be zero points in the oscillation curve.Accordingly,a series of sharp peaks appear in the TMS at the positions corresponding to these zero points.2.In this thesis,the effect of the potential barrier layer on the Seebeck coefficient and TMS thickness effect of magnetic tunnel junctions in the case of ordinary metallic ferromagnetic electrodes is investigated.The results show that the period of Seebeck coefficient oscillation with the barrier layer thickness decreases monotonically with the barrier layer periodic potential parameter;the oscillation amplitude of parallel Seebeck coefficient increases monotonically with the barrier layer periodic potential parameter,while the amplitude of anti-parallel Seebeck coefficient oscillation with the barrier layer thickness decreases monotonically with the barrier layer periodic potential parameter.The period of Seebeck coefficient oscillation with the barrier layer periodic potential parameter decreases monotonically with the barrier layer thickness,and the amplitude of oscillation increases monotonically with the barrier layer thickness.3.In this thesis,the effect of the ferromagnetic electrode of the magnetic tunnel junction on the Seebeck coefficient and the TMS thickness effect is investigated in the case of the semimetallic ferromagnetic electrode.The results show that,unlike the case of a normal metallic ferromagnetic electrode,the anti-parallel Seebeck coefficient no longer has an oscillatory effect because the semimetallic nature of the ferromagnetic electrode causes the oscillatory term of the anti-parallel state transmission coefficient to become an attenuation term,the coherence of the transmitted electron wave is destroyed: it increases monotonically with the chemical potential and decreases monotonically with the half-exchange cleavage energy.The parallel Seebeck coefficient is similar to the case of ordinary metallic ferromagnetic electrodes.4.In this thesis,the effect of the potential barrier layer of the magnetic tunnel junction on the Seebeck coefficient and TMS thickness effect is investigated in the case of a semimetallic ferromagnetic electrode.The results show that,unlike the case of ordinary metallic ferromagnetic electrodes,the anti-parallel Seebeck coefficient is basically constant with the thickness of the potential barrier layer and monotonically increasing with the periodic potential of the potential barrier layer.The parallel Seebeck coefficient is similar to the case of ordinary metallic ferromagnetic electrodes.