用外磁场控制电流感应磁化翻转效应中的临界电流方法

应用基于磁动力学方程的宏观唯象模型,研究了弱外磁场下纳米尺度赝自旋阀结构的电流感应磁化翻转效应.在统一考虑铁磁/非磁界面的自旋相关散射以及铁磁层中的自旋积累和弛豫过程后,给出了赝自旋阀结构在弱外磁场下的磁化翻转条件和临界电流.对该效应的数值计算解释了弱外磁场下赝自旋阀结构的电阻-电流回线的偏移,并给出了用外磁场控制电流感应磁化翻转效应中的临界电流方法. 关键词： 电流感应磁化翻转 外磁场 临界电流 赝自旋阀     

Symmetry ensemble theory of spin wave emitting effectdriven by current in nanoscale magnetic multilayer

<正>This paper proposes a symmetry ensemble model for the magnetic dynamics caused by spin transfer torque in nanoscale pseudo-spin-valves,in which individual spin moments in the free layer are considered as subsystems to form a spinor ensemble.The magnetization dynamics equation of the ensemble was developed.By analytically investigating the equation,many magnetization dynamics properties excited by polarized current reported in experiments,such as double spin wave modes and the abrupt frequency jump,can be successfully explained.It is pointed out that an external field is not necessary for spin wave emitting(SWE) and a novel perpendicular configuration structure can provide much higher SWE efficiency in zero magnetic field.     

Dependences of spin polarization on the control parameters in the spin-polarized injection through the magnetic p-n junction

Effective spin-polarized injection from magnetic semiconductor (MS) to nonmagnetic semiconductor (NMS) has been highlighted in recent years. In this paper we study theoretically the dependence of nonequilibrium spin polarization (NESP) in NMS during spin-polarized injection through the magnetic p-n junction. Based on the theory in semiconductor physics, a model is established and the boundary conditions are determined in the case of no external spin-polarized injection and low bias. The control parameters that may influence the NESP in NMS are indicated by calculating the distribution of spin polarization. They are the doping concentrations, the equilibrium spin polarization in MS and the bias. The effective spin-polarized injection can be realized more easily by optimizing the above parameters.     

Effects of different dopants on switching behavior of HfO_2-based resistive random access memory

In this study the effects of doping atoms(Al, Cu, and N) with different electro-negativities and ionic radii on resistive switching of HfO2-based resistive random access memory(RRAM) are systematically investigated. The results show that forming voltages and set voltages of Al/Cu-doped devices are reduced. Among all devices, Cu-doped device shows the narrowest device-to-device distributions of set voltage and low resistance. The effects of different dopants on switching behavior are explained with deferent types of CFs formed in HfO2 depending on dopants: oxygen vacancy(Vo) filaments for Al-doped HfO2 devices, hybrid filaments composed of oxygen vacancies and Cu atoms for Cu-doped HfO2 devices,and nitrogen/oxygen vacancy filaments for N-doped HfO2 devices. The results suggest that a metal dopant with a larger electro-negativity than host metal atom offers the best comprehensive performance.     

电流驱动磁化翻转中的热效应

从理论上研究了电流驱动磁开关中的热效应,在Neel-Brown弛豫时间理论和Li等的有效温度的工作基础上作了改进.在对称系综模型的Landau-Lifshitz-Gilbert和Fokker-Planck方程的基础上,分析了电流驱动磁动力学开关过程和电流引起磁势能的变化,提出一个新的电流感应磁势垒降低模型.新模型是非线性的,与Li等的有效温度模型不同.在此模型的基础上,讨论了开关临界电流对温度、开关时间的依赖关系,理论与实验相符合.对电流引起的样品温升的实验曲线进行了修正,实验结果与文中的非线性势垒降低模 关键词： 热效应 自旋传输矩 Neel-Brown弛豫时间 Fokker-Planck方程     

电动流动分析的色谱分离研究

建立了一种基于增压电渗泵驱动、整体柱分离和紫外检测相结合的电动流动分析系统。研究了载流溶液中甲醇的体积分数对电渗泵空载流量、输出压强、移动相流量和分离度的影响。在4950V的外加电压下,以含0.5mmol/L六亚甲基四胺的45%甲醇溶液为泵载流,电渗泵的流量和输出压强分别为0.58mL/min和0.79MPa,以泵载流为流动相,该系统对苯和萘进行了反相色谱分离。电动流动分析系统设备简单、操作方便、功能多样。对苯和萘的分离结果表明,电动流动分析系统可用于样品的色谱分离。     

便携式电动流动分析系统同时富集测定矿泉水中铬(Ⅵ)和镉(Ⅱ)

研究了电渗泵性能的改进以及双向电堆积系统各种参数对富集倍数的影响。提出一种电渗驱动与双向电堆积相结合的便携式电动流动分析系统,并采用石墨炉原子吸收法对矿泉水中铬(Ⅵ)和镉(Ⅱ)进行了同时富集和测定。检出限为9ng/L Cr(Ⅵ)和10ng/L Cd(Ⅱ)(n=11,3倍空白标准偏差)。加入相当于样品含量的Cr(Ⅵ)和Cd(Ⅱ),回收率分别为(105～107)±2％和(104～106)±2％(n=3)。     

Ni/HfO_2/Pt阻变单元特性与机理的研究

研究了Ni/HfO2(10 nm)/Pt存储单元的阻变特性和机理.该器件具有forming-free的性质,还表现出与以往HfO2(3 nm)基器件不同的复杂的非极性阻变特性,并且具有较大的存储窗口值(105).存储单元的低阻态阻值不随单元面积改变,符合导电细丝阻变机理的特征.采用X射线光电子能谱仪分析器件处于低阻态时的阻变层HfO2薄膜的化学组分以及元素的化学态,结果表明,Ni/HfO2/Pt阻变存储器件处于低阻态时的导电细丝是由金属Ni导电细丝和氧空位导电细丝共同形成的.     

一种电色谱整体微柱的制备及其分离性能

毛细管电色谱具有很高的分离效率，但也存在一些缺点，如浓度检出限差、柱容量低和工作电压太高等。为了克服这些缺点，我们在2．7mm内径的石英管内用石英砂填充硅酸钾。甲酰胺聚合整体柱，并进行了电色谱分离的可行性研究。实验结果证明这种方法是可行的。它限制了热效应，可使用常规分析仪器检测，所需工作电压不超过1000V。     

基于磁动力学方程的电流感应磁化翻转效应的宏观模型

提出了一个基于磁动力学方程的宏观唯象理论模型，对纳米级赝自旋阀结构的电流感应磁化翻转效应给出了明晰的物理解释：流入自由层的净自旋流和自由层内的自旋弛豫过程的共同作用，导致自由层总磁矩随时间的改变，甚至产生磁化方向的翻转.模型将“铁磁/非铁磁”界面的自旋相关散射，以及铁磁层中的自旋积累和弛豫过程，统一于宏观的磁动力学方程中.通过求解该方程的解析解，给出了赝自旋阀在电流激励下的磁化翻转条件和临界电流密度的表达式.对该效应的定性解释和数值模拟结果都和实验报道良好符合.根据模型分析了影响临界电流密度的诸因素，并指出提高器件性能的途径. 关键词： 电流感应磁化翻转 磁动力学方程 自旋电子学