Enhanced energy storage behaviors in free-standing antiferroelectric Pb(Zr_(0.95)Ti_(0.05))O_3 thin membranes

Free-standing antiferroelectric Pb(Zr_(0.95)Ti_(0.05)O_3(PZT(95/5)) thin film is fabricated on 200-nm-thick Pt foil by using pulsed laser deposition.X-ray diffraction patterns indicate that free-standing PZT(95/5) film possesses an α-axis preferred orientation.The critical electric field for the 300-nm-thick free-standing PZT(95/5) film transiting from antiferroelectric to ferroelectric phases is increased to 770 kV/cm,but its saturation polarization remains almost unchanged as compared with that of the substrate-clamped PZT(95/5) film.The energy storage density and energy efficiency of the substrate-clamped PZT(95/5) film are 6.49 J/cm~3 and 54.5%,respectively.In contrast,after removing the substrate,the energy storage density and energy efficiency of the free-standing PZT(95/5) film are enhanced up to 17.45 J/cm~3 and 67.9%,respectively.     

柔性磁性薄膜材料与器件研究进展

近年来,随着物联网、仿生机器人、移动式医疗健康等领域的兴起,柔性电子材料和器件受到广泛关注.基于磁性材料构建的传感器和存储器是电子器件的重要组成部分.随着柔性薄膜材料制备技术的发展,人们已经制备出高质量的柔性乃至可拉伸的磁性金属和氧化物薄膜,它们展现的不仅是更强的变形能力,还有新的物理效应与响应规律.研究结果表明,柔性磁电子器件在非接触传感、高灵敏应变探测、超分辨触觉感知等方面展现出独特的优势,具有广阔的应用前景.本文主要从柔性磁性材料的制备、物性调控规律和器件应用方面综述这一新兴领域的发展动态,并对其未来的发展趋势进行展望.     

乙烯类聚合物-炭黑复合物的PTC效应

本文以低密度聚乙烯(LDPE)和乙烯-醋酸乙烯酯共聚物(EVA)为基材,炭黑(CB)为导电微粒,探讨了聚合物-炭黑复合物的结构对正温度系数效应(PTC)增强与减弱的影响和炭黑含量与PTC效应的关系以及交联结构对PTC现象的稳定作用.     

Modulation of physical properties of oxide thin films by multiple fields

Recent studies of the modulation of physical properties in oxide thin films by multiple fields are reviewed.Some of the key issues and prospects of this area of study are also addressed.Oxide thin films exhibit versatile physical properties such as magnetism,ferroelectricity,piezoelectricity,metal–insulator transition(MIT),multiferroicity,colossal magnetoresistivity,switchable resistivity.More importantly,the exhibited multifunctionality can be tuned by various external fields,which has enabled demonstration of novel electronic devices.     

Effect of thermal deformation on giant magnetoresistance of flexible spin valves grown on polyvinylidene fluoride membranes

We fabricated flexible spin valves on polyvinylidene fluoride(PVDF) membranes and investigated the influence of thermal deformation of substrates on the giant magnetoresistance(GMR) behaviors. The large magnetostrictive Fe_(81)Ga_(19)(Fe Ga) alloy and the low magnetostrictive Fe_(19)Ni_(81)(Fe Ni) alloy were selected as the free and pinned ferromagnetic layers.In addition, the exchange bias(EB) of the pinned layer was set along the different thermal deformation axes α_(31) or α_(32) of PVDF. The GMR ratio of the reference spin valves grown on Si intrinsically increases with lowering temperature due to an enhancement of spontaneous magnetization. For flexible spin valves, when decreasing temperature, the anisotropic thermal deformation of PVDF produces a uniaxial anisotropy along the α_(32) direction, which changes the distribution of magnetic domains. As a result, the GMR ratio at low temperature for spin valves with EB α_(32)becomes close to that on Si, but for spin valves with EB α_(31)is far away from that on Si. This thermal effect on GMR behaviors is more significant when using magnetostrictive Fe Ga as the free layer.     

具有条纹磁畴结构的NiFe薄膜的制备与磁各向异性研究

具有条纹磁畴结构的磁性薄膜表现出面内转动磁各向异性,对于解决高频电子器件的方向性问题起着至关重要的作用.本文采用射频磁控溅射的方法,研究了NiFe薄膜的厚度、溅射功率密度、溅射气压等制备工艺参数对条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律.研究发现,在功率密度15.6 W/cm~2与溅射气压2 mTorr(1 Torr=1.33322×102Pa)下生长的NiFe薄膜,表现出条纹磁畴的临界厚度在250 nm到300 nm之间.厚度为300 nm的薄膜比250 nm薄膜的垂直磁各向异性场增大近一倍,从而磁矩偏离膜面形成条纹磁畴结构,并表现出面内转动磁各向异性.高溅射功率密度可以降低薄膜出现条纹磁畴的临界厚度.在相同功率密度15.6 W/cm~2下生长300 nm的NiFe薄膜,随着溅射气压由2 mTorr增大到9 mTorr,NiFe薄膜的垂直磁各向异性场逐渐由1247.8 Oe(1 Oe=79.5775 A/m)增大到3248.0 Oe,面内转动磁各向异性场由72.5 Oe增大到141.9 Oe,条纹磁畴周期从0.53μm单调减小到0.24μm.NiFe薄膜的断面结构表明柱状晶的形成是表现出条纹磁畴结构的本质原因,高功率密度下低溅射气压有利于柱状晶结构的形成,表现出规整的条纹磁畴结构,高溅射气压会导致柱状晶纤细化,面内转动磁各向异性与面外垂直磁各向异性增强,条纹磁畴结构变得混乱.