Strain-mediated magnetoelectric control of tunneling magnetoresistance in magnetic tunneling junction/ferroelectric hybrid structures

Because of the wide selectivity of ferromagnetic and ferroelectric (FE) components, electric-field (E-field) control of magnetism via strain mediation can be easily realized through composite multiferroic heterostructures. Here, an MgO-based magnetic tunnel junction (MTJ) is chosen rationally as the ferromagnetic constitution and a high-activity (001)-Pb(Mg$_{1/3}$Nb$_{2/3}$)$_{0.7}$Ti$_{0.3}$O$_{3}$ (PMN-0.3PT) single crystal is selected as the FE component to create a multiferroic MTJ/FE hybrid structure. The shape of tunneling magnetoresistance (TMR) versus in situ E-fields imprints the butterfly loop of the piezo-strain of the FE without magnetic-field bias. The E-field-controlled change in the TMR ratio is up to $-$0.27% without magnetic-field bias. Moreover, when a typical magnetic field ($\sim \pm 10$ Oe) is applied along the minor axis of the MTJ, the butterfly loop is changed significantly by the E-fields relative to that without magnetic-field bias. This suggests that the E-field-controlled junction resistance is spin-dependent and correlated with magnetization switching in the free layer of the MTJ. In addition, based on such a multiferroic heterostructure, a strain-gauge factor up to approximately 40 is achieved, which decreases further with a sign change from positive to negative with increasing magnetic fields. This multiferroic hybrid structure is a promising avenue to control TMR through E-fields in low-power-consumption spintronic and straintronic devices at room temperature.     

流体/准饱和多孔介质中伪Scholte波的传播特性

研究流体/多孔介质界面Scholte波的传播特性对于水下勘探、地震工程等领域具有重要意义.本文基于Biot理论和等效流体模型,采用势函数方法,推导了描述有限厚度流体/准饱和多孔半空间远场界面波的特征方程和位移、孔压计算公式.在此基础上,分别以砂岩和松散沉积土为例,研究了流体/硬多孔介质和流体/软多孔介质两种情况下,可压缩流体层厚度和多孔介质饱和度对伪Scholte波传播特性的影响.结果表明：多孔介质软硬程度显著影响界面波的种类、相速度、位移和水压力分布;有限厚度流体/饱和多孔半空间界面处伪Scholte波相速度与界面波波长和流体厚度的比值有关;孔隙水中溶解的少量气体对剪切波的相速度的影响不大,对压缩波相速度、伪Scholte波相速度和孔隙水压力分布影响显著.     

原子力显微镜在PLD法制备ZnO薄膜表征中的应用

利用脉冲激光沉积(PLD)法在氧压为16 Pa、衬底温度为400~700 ℃时,在单晶Si(100) 衬底上制备ZnO薄膜,并通过原子力显微镜(AFM)、X射线衍射(XRD)谱和光致发光谱对制得的薄膜样品进行表面形貌、结构特性和发光性质研究。其中通过原子力显微镜对样品的二维、三维以及剖面线图进行了分析。结果表明衬底温度700 ℃时得到的薄膜样品表面较均匀致密,晶粒生长较充分,结晶质量较高,相对发光强度高。控制氧压为5.7 Pa,在衬底温度为600 ℃,沉积时间分别为10,20,45 min制备ZnO薄膜样品;利用原子力显微镜对样品进行表面形貌观察,得知只有沉积时间足够长才能使薄膜表面晶粒充分生长。     

化学计量比LiNbO3晶体的激光显微拉曼光谱研究

对用助熔剂提拉法生长的近化学计量比LiNbO3晶体进行了激光显微拉曼光谱测试分析,与同成分LiNbO3晶体相比较,A1(TO)与E(TO)模的谱线数目、频率基本不变,验证了LiNbO3晶体属置换式固溶体的结论.738cm-1处拉曼振动峰（A1(LO)模）的相对强度随晶体中Li2O含量的增加发生了明显的变化,在两种掺杂晶体中,此振动峰已经消失.根据Li空位模型,从占位和结构上进行了分析讨论.在152和872cm-1处拉曼振动峰半高宽随晶体中Li/Nb的增大而变窄,对二者关系进行了线性拟合,利用拟合公式可根据拉曼振动峰半高宽计算晶体中的Li/Nb值. 关键词： 化学计量比 拉曼光谱 线性拟合 半高宽     

Chalcogenide Perovskite YScS_3 as a Potential p-Type Transparent Conducting Material

Transparent conducting materials(TCMs) have been widely used in optoelectronic applications such as touchscreens,flat panel displays and thin film solar cells.These applications of TCMs are currently dominated by n-type doped oxides.High-performance p-type TCMs are still lacking due to their low hole mobility or p-type doping bottleneck,which impedes efficient device design and novel applications such as transparent electronics.Here,based on first-principles calculations,we propose chalcogenide ...     

Facile Mechanochemical Green Fabrication of CuBr(tu)_3 Nanowires as Electrochemical Supercapacitor Electrodes

CuBr(tu)_3 nanowires(tu: thiourea) was prepared by a facile mechanochemical green method for the first time and their application as electrode for supercapacitors is also studied. The as-prepared CuBr(tu)_3 nanowires show length of around 4 μm and width of 50~60 nm. Those nanowires exhibited high specific capacitance of 1408 F·g~(-1) at a scan rate of 5 mV·s~(-1) and 1683 F·g~(-1) at current density of 10 A·g~(-1) in a 2M KOH electrolyte. This study provides a simple, efficient, and environmental strategy to fabricate novel nanoscale electrode materials constructing metal-organic frameworks.     

~3He恒温器减压池抽气管路的解析特征

本文提出设计~3He恒温器减压池抽气管路的解析方法,并且发现管路具有截止直径等物理特征。以及论证了0.2K是~3He恒温器的极限温度。     

PAn/PEO-LiClO4界面的交流阻抗研究

近年来,交流阻抗方法已成功地应用于固体电极-电解质界面电化学性能的研究.特别是最近几年,聚氧化乙烯-锂盐复合物(PEO-LiX)系列高分子电解质材料研究的深入,研制以高分子电解质为隔膜的全固态锂电池的设想已成可能.前人用交流阻抗方法对Li/PEO-LiX和钒氧阴极/PEO-LiX界面行为研究已作了大量工作,并获得相关锂电池电极界面电化学性能的理论数据.本文用化学氧化法合成聚苯胺(PAn)阴极材料和本室改进的PEO-LiClO_4复合物作室温固体电解质,研究PAn/PEO-LiClO_4电极界面的电化学性能,获得一些新的结果。     

光导纤维光谱法——Ⅴ.光导纤维化学传感器

本文介绍了光导纤维化学传感器的基本原理,传光型和传感型化学传感器的各种探头设计和构型,以及它们在无机和有机分析方面的应用。涉及参考文献105篇。