| Multiferroic magnetoelectric films have both ferroelectricity and ferromagnetism,and the conversion between electricity and magnetism can be realized through the coupling between multiferroic properties,which is of great significance to promote the development of new memory devices.In this dissertation,the multilayer Ba(Zr0.2Ti0.8)O3-0.5(Ba0.3Ca0.7)Ti O3/Fe70Ga30(BZT-0.5BCT/Fe Ga)composite film structure was constructed.The resistance status of the BZT-0.5BCT/Fe Ga composite films were adjusted by applying bias electric field to realize memory function.The research contents are as follows:First,BZT-0.5BCT films were prepared by magnetron sputtering.The piezoelectric properties of BZT-0.5BCT films were optimized by optimizing annealing temperature,Ar/O2ratio and the sputtering pressure,effect of top electrodes on the properties of BZT-0.5BCT films were also discussed.The results show that the films prepared with annealing temperature of 500°C and the pressure of 1.5 Pa with Ar to O2ratio of 30:20 exhibit the best piezoelectric properties,and the piezoelectric displacement is 64.2?.The top electrode has great influence on the ferroelectric properties of BZT-0.5BCT films,but has little influence on the piezoelectric displacement.Fe Ga films with different thickness were prepared on BZT-0.5BCT by using magnetron sputtering and ion beam sputtering combined with photolithography.The effect of bias voltage on the resistance state of different thickness Fe Ga ferromagnetic layer were investigated,and the magnetic anisotropy of BZT-0.5BCT/Fe Ga composite films were studied.By applying bias voltage to ferromagnetic layer with different thickness,when the thickness is 25 nm,40 nm,60 nm,80 nm,105 nm and 120 nm,the change rate of resistance is 20%,26%,21%,20.5%,16.8%and 20.14%,respectively.The control of resistance state with bias voltage for ferromagnetic layer with different thickness is realized,and the control effect of bias voltage increases with the decrease of thickness.Finally,different sizes of Fe Ga films were prepared on BZT-0.5BCT films by using magnetron sputtering combined with photolithography.The memory device cells based on laminated ferroelectric/ferromagnetic composite structure were constructed.The ferroelectric and ferromagnetic properties of BZT-0.5BCT/Fe Ga composite films were studied,and the effect of bias voltage on the resistance state of different sizes of ferromagnetic layer was emphatically explored.The obvious domain structure of BZT-0.5BCT ferroelectric layer and Fe Ga ferromagnetic layer were observed.By applying bias voltage to the ferromagnetic layer of BZT-0.5BCT/Fe Ga composite films with different sizes,the control effect of the bias voltage on the resistance state of ferromagnetic layer is realized,and with the decrease of the size,the resistance change ratio increases. |
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