磁电阻效应的计算机辅助测试

概述了薄膜磁电阻效应的测试原理，着重分析了利用计算机实现磁电阻效应测试的智能化软件ＭＲＣＡＴ（Ｍａｇｎｅｔｏｒｅｓｉｓｔａｎｃｅ Ｃｏｍｐｕｔｅｒ Ａｉｄｅｄ Ｔｅｓｔ Ｓｙｓｔｅｍ）的设计。该系统集数据采样、数据处理、参数计算等功能于一体，具有交互性强、用户界面友好等特点。同时ＭＲＣＡＴ系统还能在计算机屏蔽、打印机上绘出被测样品的磁电阻效应曲线，并生成标准ＰＣＸ图象文件以供引用。     

Guided Molecular Assembly on a Locally Reactive 2D Material

Atomically precise engineering of the position of molecular adsorbates on surfaces of 2D materials is key to their development in applications ranging from catalysis to single‐molecule spintronics. Here, stable room‐temperature templating of individual molecules with localized electronic states on the surface of a locally reactive 2D material, silicene grown on ZrB₂, is demonstrated. Using a combination of scanning tunneling microscopy and density functional theory, it is shown that the binding of iron phthalocyanine (FePc) molecules is mediated via the strong chemisorption of the central Fe atom to the sp³‐like dangling bond of Si atoms in the linear silicene domain boundaries. Since the planar Pc ligand couples to the Fe atom mostly through the in‐plane d orbitals, localized electronic states resembling those of the free molecule can be resolved. Furthermore, rotation of the molecule is restrained because of charge rearrangement induced by the bonding. These results highlight how nanoscale changes can induce reactivity in 2D materials, which can provide unique surface interactions for enabling novel forms of guided molecular assembly.     

Optochemically Responsive 2D Nanosheets of a 3D Metal–Organic Framework Material

Outstanding functional tunability underpinning metal–organic framework (MOF) confers a versatile platform to contrive next‐generation chemical sensors, optoelectronics, energy harvesters, and converters. A rare exemplar of a porous 2D nanosheet material constructed from an extended 3D MOF structure is reported. A rapid supramolecular self‐assembly methodology at ambient conditions to synthesize readily exfoliatable MOF nanosheets, functionalized in situ by adopting the guest@MOF (host) strategy, is developed. Nanoscale confinement of light‐emitting molecules (as functional guest) inside the MOF pores generates unusual combination of optical, electronic, and chemical properties, arising from the strong host–guest coupling effects. Highly promising photonics‐based chemical sensing opened up by the new guest@MOF composite systems is shown. By harnessing host–guest optochemical interactions of functionalized MOF nanosheets, detection of an extensive range of volatile organic compounds and small molecules important for many practical applications has been accomplished.     

Controlling Structural Anisotropy of Anisotropic 2D Layers in Pseudo‐1D/2D Material Heterojunctions

Chemical vapor deposition and growth dynamics of highly anisotropic 2D lateral heterojunctions between pseudo‐1D ReS₂ and isotropic WS₂ monolayers are reported for the first time. Constituent ReS₂ and WS₂ layers have vastly different atomic structure, crystallizing in anisotropic 1T′ and isotropic 2H phases, respectively. Through high‐resolution scanning transmission electron microscopy, electron energy loss spectroscopy, and angle‐resolved Raman spectroscopy, this study is able to provide the very first atomic look at intimate interfaces between these dissimilar 2D materials. Surprisingly, the results reveal that ReS₂ lateral heterojunctions to WS₂ produce well‐oriented (highly anisotropic) Re‐chains perpendicular to WS₂ edges. When vertically stacked, Re‐chains orient themselves along the WS₂ zigzag direction, and consequently, Re‐chains exhibit six‐fold rotation, resulting in loss of macroscopic scale anisotropy. The degree of anisotropy of ReS₂ on WS₂ largely depends on the domain size, and decreases for increasing domain size due to randomization of Re‐chains and formation of ReS₂ subdomains. Present work establishes the growth dynamics of atomic junctions between novel anisotropic/isotropic 2D materials, and overall results mark the very first demonstration of control over anisotropy direction, which is a significant leap forward for large‐scale nanomanufacturing of anisotropic systems.     

Angular Magnetoresistance Oscillations in Q1D as Interlayer Aharonov-Bohm Interference

We present a unified visual picture of magnetoresistance oscillations in Q1D conductors for a general orientation of a magnetic field. We give an intuitive geometrical interpretation of the two-parameter pattern of oscillations as an Aharonov-Bohm interference effect in the interlayer electron tunneling.     

坐标测量机空间测量不确定度分析方法

论述了影响坐标测量机空间测量不确定度的２１个单项几何误差以及它们对空间测量不确定度的传递关系。依此可推出空间测量不确定度表达式Ｕ９５＝Ｋ１＋Ｌ／·Ｋ２。文后给出了分析实例。这对坐标测量机的研制工作有指导意义。     

Magnetoresistance and variable range hopping conductivity in n-CuInSe2

Variable range hopping conduction of Mott type is observed in n-type CuInSe₂ in two temperature ranges. These are below 20 K and the other, above this temperature, up to 45 K, that have different values of the parameters ρ_o and T_o in the relation ρ = ρ_o exp [T_o/T]^S. This type of conduction is also found at different fixed magnetic field up to 35 T. The temperature and magnetic field dependence of the magnetoresistance in both weak and strong field regimes are analyzed in the framework of the Efros and Shklovskii model. The observed departure of the hopping parameters at low temperatures from the expected theoretical prediction is explained as due to the presence of negative magnetoresistance at lower fields and the effect of saturation of the positive magnetoresistance at higher fields.     

Synergetic Behavior in 2D Layered Material/Complex Oxide Heterostructures

The marriage between a 2D layered material (2DLM) and a complex transition metal oxide (TMO) results in a variety of physical and chemical phenomena that cannot be achieved in either material alone. Interesting recent discoveries in systems such as graphene/SrTiO₃, graphene/LaAlO₃/SrTiO₃, graphene/ferroelectric oxide, MoS₂/SrTiO₃, and FeSe/SrTiO₃ heterostructures include voltage scaling in field‐effect transistors, charge state coupling across an interface, quantum conductance probing of the electrochemical activity, novel memory functions based on charge traps, and greatly enhanced superconductivity. In this context, various properties and functionalities appearing in numerous different 2DLM/TMO heterostructure systems are reviewed. The results imply that the multidimensional heterostructure approach based on the disparate material systems leads to an entirely new platform for the study of condensed matter physics and materials science. The heterostructures are also highly relevant technologically as each constituent material is a promising candidate for next‐generation optoelectronic devices.     

Magnetoresistance effect of bismuth in a quantizing field

The magnetoresistance effect in bismuth has been studied at the very low temperature limit when the lattice scattering is dominant in solids. Results show that the magnetoresistance oscillates with the dc magnetic field and displays sharp, cusplike discontinuities due to the nonlinear and singular properties of the energy band structure of bismuth for the modified nonellipsoidal, nonparabolic (MNENP) model.     

Na0．75Co1-xErxO2的磁电阻

NaxCoO2具有奇异热电性质和电磁性质的强关联体系。为进一步探索材料中的电磁性质,制备出Na0．75Co1-xErxO2（0≤x≤0．10）多晶样品。对系统的电阻率、磁电阻和磁化率进行测量,结果显示,加磁场后系统的电阻减小,表明磁性离子对传导电子的散射作用;有效磁矩会随着Er的掺杂浓度增加迅速增大,3％的Er掺杂就能使有效磁矩几乎增大一倍;当系统的磁电阻达到15％,意味着Er的掺杂导致系统出现异常的电磁性质。     

Magnetoresistance of RuO2-Based Thick Film Resistors

In a series of samples whose composition was systematically changed, we have studied the magnetoresistance (R/R = [R(B)-R]/R) of RuO ₂ -based thick film resistors (TFR's) in magnetic fields (B) up to 20 Tesla and in a temperature range (1.2 K < T < 40 K) in which their resistance exhibits insulating behavior at the boundary between the strong and the weak localization. At the higher temperatures, R/R exhibits a positive bump that does not depend on the RuO ₂ concentration but it changes with the concentration of magnetic Mn impurities diluted in the glassy matrix. For T 20 K magnetoresistance is entirely negative and it has a quadratic magnetic field dependence at low field. We use the weak localization theory to relate these features of the high temperature magnetoresistance to the composition of TFR's. At low temperature (T < 4.2 K) the negative magnetoresistance shows some peculiarities. The quadratic term shrinks within a vanishing magnetic field range and the magnetoresistance linearly increases in a wide range of B. At the strongest fields and the lowest temperature R/R shows a tendency to saturation. Although these results do not enable to discriminate among different mechanisms, we note that the low temperature (T < 4.2 K) behavior is essentially consistent with recent theory of Nguen et al.     

Intergranular corrosion in electrochemical machining

In a study of electrochemical drilling, the influence of the electrolyte composition on intergranular corrosion of various nickel alloys and of hardenable stainless steel was investigated. The nickel-base alloys remained unaffected in a solution of 15 % NaNO₃ + 20 % NaClO₃ + 65 % H₂O but suffered intergranular corrosion in solutions of NaNO₃ and NaNO₃ + NaCl. Stainless steel showed no signs of intergranular attack in any of the electrolyte solutions used.     

Intergranular structure in dental amalgams

The existence of an intergranular precipitate that provides a structural basis of creep, intergranular corrosion and thermal instability in dental amalgams has been in dispute. Also in dispute is a related matter concerning the solid solubility of Sn in ₁. Both these aspects have been examined in this differential scanning calorimetry (DSC) study using the following materials: (a) a conventional ₂–containing amalgam, (b) six ₂–free amalgams, and (c) a series of ₁ specimens with up to 4 wt% Sn. It has been observed that the solid solubility of Sn in ₁ is about 1.0 wt%. Above this Sn concentration, an intergranular precipitate, identified as the ₂ phase of the SnHg system, appears in ₁. This phase is characterized by a low melting temperature (90°C). The existence of this phase in the conventional dental amalgam has been confirmed. It has been observed further that the ₂–free dental amalgams, depending on their nature and Hg contents, may contain ₂ either as a transient or a permanent phase.     

Magnetoresistance effect in a graphene modulated by magnetic-electrical barriers

We theoretically investigate the magnetoresistance (MR) effect in a monolayer graphene modulated by both magnetic and electrical barriers, which can be experimentally realized by depositing two parallel metallic ferromagnetic tripes under an applied voltage on the top and bottom of a graphene. The tremendous MR can be found due to the significant difference between the transmissions through the parallel and antiparallel magnetization configurations, and the MR ratio strongly depends on the strength of the magnetic field and the height of the electric barrier. Therefore, we can control the MR effect by changing either of the two magnetic fields or the electric barrier to make a MR device based on a graphene.     

Intergranular corrosion of a stud used in safety relief valve

In the present paper, a failure case study on intergranular corrosion of stainless steel stud is discussed. The stud was in the assembly under marine environment, for a period of 11 years. Detailed investigation revealed that the crack had propagated in an intergranular manner, after initiation at threaded region of the stud, leaving behind widespread grain dissolution. The presence of chloride ions in deposits on central region of stud, exposed to marine environment was also established. The high carbon content, coupled with exposure to sensitization range of stainless steel during processing caused corrosion along intergranular corrosion.This paper brings out the details of investigation carried out on the failed stud.     

Intrinsic Negative Magnetoresistance in Van Der Waals FeNbTe2 Single Crystals

Magnetoresistance, the dependence of resistivity on the applied magnetic field, provides the opportunity to manipulate and utilize the electronic spin degree of freedom, which is not only a long‐term frontier field of solid‐state physics but also the cornerstone of information storage technology. However, the negative magnetoresistance (nMR) is a relatively rare case of magnetoresistance in which the microscopic origin is still elusive and for which it is difficult to define a general interpretation. Herein, an experimental case of an intrinsic unsaturated nMR is demonstrated in van der Waals FeNbTe₂ single crystal. The clear‐cut evidence in angle‐resolved photoemission spectroscopy (ARPES), the electronic transport measurement, and DC/AC magnetic susceptibility confirms that the intrinsic unsaturated nMR is derived from the comprehensive effect of Anderson localization and a spin glass state. Taking into consideration that intrinsic unsaturated nMR has so far been rarely reported, especially in van der Waals structures, it is anticipated that this work will not only lead to a deep understanding of the inherent microcosmic mechanism but will also serve as a guide to broaden the research of spintronics and information storage based on magnetoresistance.