Investigation On Preparation And Magnetoelectric Properties Of Antiferroelectric PLZST/LSMO Composite Thin Films

With the continuous development of human civilization,intelligence has become the mainstream development direction of today’s science and technology.Functional materials,as an important support for artificial intelligence,have also become a hot topic today.Among all the functional materials,magnetoelectric materials,which can respond to magnetic and electrical signals simultaneously,have received extensive attention since the discovery.The magnetoelectric composite films made of ferroelectric and ferromagnetic materials have received extensive attention for their unique advantages,include high magnetoelectric coupling coefficient,high perform temperature,mechanism research and miniaturization.Compared with ferroelectric materials,antiferroelectrics can undergo antiferroelectric-ferroelectric phase transition under certain electric field,temperature and/or stress,and thus have both ferroelectric and antiferroelectric states.In theory,the magnetoelectric composite films made of antiferroelectric and ferromagnetic materials will have more abundant physical connotation,and gradually attract the attention of researchers.In this work,La_0.7Sr_0.3MnO₃ was selected as the ferromagnetic layer and(Pb_0.97La_0.02)(Zr_0.66Sn_0.23Ti)O₃ was selected as the antiferroelectric layer to construct the2-2 type magnetoelectric composite thin films.The effects of the preparation process,substrate and other factors on the magnetic,electrical and magnetodielectric properties of the films were systematically studied.The main research contents and innovative achievements of this article are listed as follows:（1）LSMO thin films were prepared on Si substrate by chemical solution method.The films exhibited good magnetic and electrical properties.The saturation polarization and Curie temperature of the film under the external magnetic field of 500 Oe were 220emu/cm3 and 334 K,respectively.The resistivity of the film at room temperature was0.14Ω·cm.（2）PLZST thin films were prepared by chemical solution method.The effects of different annealing temperature,time,capping layer and thickness on the microstructure and electrical properties of the films were systematically studied.The study identified:（a）The most suitable annealing process for the PLZST films is annealing at 700°C for 30 minutes;（b）The presence of the capping layer can effectively avoid the deterioration of the PLZST film due to lead loss.The films with capping layer achieved an increases by 25.4%of dielectric constant and an increases by 29.1%of the saturation polarization;（c）As the film thickness increases from 234 nm to 532 nm,the substrate’s stress on the film weakened.The remnant polarization decreased by 28.3%,ΔE decreased by 34%,and the energy storage efficiency increased from 66.4%to68.8%.However,the decrease in the thre caused the energy storage density of the film decreasing from 7.9 J/cm³ to 6.7 J/cm³.（3）LSMO thin films were prepared on Al₂O₃ substrates by chemical solution method,and the magnetic and electrical properties of LSMO/Si and LSMO/Al₂O₃ thin films were compared:（a）LSMO/Al₂O₃ thin films had higher saturation magnetization（260 emu/cm3）,lower coercive field（27.5 Oe）,higher Curie temperature（346 K）;（b）LSMO/Al2O3 films had lower resistivity of 0.09Ω·cm at room temperature and higher metal-insulation transition temperature（258 K）;（c）Magnetoresistance of LSMO/Si at50 K and room temperature were-12.0%and-26.8%,respectively.The magnetoresistance of LSMO/Al₂O₃ at 50 K and room temperature were-12.9%and-28.7%,respectively.（4）PLZST/LSMO composite films were prepared on Si substrate and Al₂O₃substrates by chemical solution method,respectively.The properties of the two films were compared:Studies showed that compared to PLZST/LSMO/Si composite films,PLZST/LSMO/Al₂O₃ composite films had superior electrical and magnetodielectric effects.The PLZST/LSMO/Al₂O₃ composite films had a high breakdown field of 4.0MV/cm,an energy storage density of 46.3 J/cm³,an energy storage efficiency of 88.4%,a dielectric tuning ratio of 75.9%,and a magnetodielectric value of 2.51%at room temperature.And the magnetodielectric effect of PLZST/LSMO/Al₂O₃ composite films at low temperature（50K）achieved 20.1%.What’s more,The PLZST/LSMO/Al₂O₃composite film also had more excellent fatigue stability.