Magneto-optical Kerr Effect of Mono-layer NiX_(2)(X=Cl,Br,I):A Density Functional Theory Study

The full-potential linearized augmented plane wave plus local orbital method is utilized for exploring the electronic,magnetic,and magneto-optical properties of the NiX_(2)(X=Cl,Br,and I)single layer.The first-principles calculation demonstrates that these compounds are ferromagnetic indirect semiconductors,and the energy band gaps of NiX_(2)for X=Cl,Br,and I are 3.888,3.134,and 2.157 eV,respectively.The magnetic moments of Ni atoms in NiX_(2)monolayer are 1.656,1.588,1.449μB,and their magneto-crystalline anisotropy energies are 0.167,0.029,0.090 meV,respectively.Based on the macro-linear response theory,we systematically studied the influences of the external magnetic field and out-of-plane strain on the magneto-optical Kerr effect(MOKE)spectrum of the NiX_(2)single layer.It is found that,when the external magnetic field is perpendicular to the sample plane,the value of the Kerr rotation angle reaches the maximum,and the single-layer NiI_(2)material has a Kerr rotation angle of 1.89°at the photon energy of 1.986 eV.Besides,the Kerr rotation spectrum of NiCl_(2)and NiBr_(2)monolayers redshift as the out-of-plane strain increases,while NiI_(2)monolayer blueshifts.Accurate computation of the MOKE spectrum of NiX_(2)materials provides an opportunity for applications of 2D magnetic material ranging from sensing to data storing.

不同栅氧退火工艺下的SiC MOS电容及其界面电学特性

SiC MOS电容的电学特性和栅氧界面特性是评价和改进SiC MOS器件制造工艺的重要依据。通过依次测试SiC MOS器件的氧化物绝缘特性、界面态密度、偏压温度应力不稳定性(偏压温度应力条件下的平带电压漂移)、氧化物陷阱电荷密度和可动电荷密度的方法,对分别经过氮等离子体氧化后退火(POA)处理、氮氢混合等离子体POA处理、氮氢氧混合等离子体POA处理、氮氢氯混合等离子体POA处理的SiC MOS电容的电学特性和栅氧界面特性进行了分析。结果表明,该方法可以系统地评价SiC MOS电容电学特性和栅氧界面特性,经过氮氢氯混合等离子体POA处理的SiC MOS电容可以满足高温、大场强下长期运行的性能指标。

Compact magneto-optical traps using planar optics

Magneto-optical traps (MOTs) composed of magnetic fields and light fields have been widely utilized to cool andconfine microscopic particles. Practical technology applications require miniaturized MOTs. The advancement of planaroptics has promoted the development of compact MOTs. In this article, we review the development of compact MOTs basedon planar optics. First, we introduce the standardMOTs. We then introduce the gratingMOTs with micron structures, whichhave been used to build cold atomic clocks, cold atomic interferometers, and ultra-cold sources. Further, we introducethe integrated MOTs based on nano-scale metasurfaces. These new compact MOTs greatly reduce volume and powerconsumption, and provide new opportunities for fundamental research and practical applications.

Influence of Magnetic Field Inhomogeneity on a Magneto-Optical Current Sensor

The growth in the capacity of electric power system creates a demand for the protection of relaying systems. Optical current transducers—OCT that are mainly made up of single mode optical fibers which are subjected to Faraday rotation are used as a replacement for electromagnetic transducers due to their immunity to electromagnetic interference. However, the principal parameter in this system, the sensitivity to magnetic fields or current, depends on the Verdet constant, which is low in the case of optical fibers. However, the optical path length can be increased to compensate for it by winding the fiber around a current carrying element a large number of turns. In this work, we study a current sensor, which is made up of a conductor coil with a fiber inside, thus increasing sensitivity. We study the effect of the inhomogeneity of the magnetic field induced by the current on the sensitivity of the optical fiber sensor.

Resonant magneto-optical Kerr effect induced by hybrid plasma modes in ferromagnetic nanovoids

With nanovoids buried in Co films, resonant structures were observed in spectra of polar magneto-optical Kerr effect（MOKE）, where both a narrow bandwidth and high intensity were acquired. Through changing the thickness of Co films and the lattice of voids, different optical modes were introduced. For a very shallow array of voids, the resonant MOKE was induced by Ag plasma edge resonance, for deeper ones, hybrid plasma modes, such as void plasmons in the voids, surface lattice plasmons between the voids, and the co-action of them, etc. resulted in resonant MOKE. We found that resonant MOKE resulted from the void plasmons resonance which possesses the narrowest bandwidth for the lowest absorption of voids. The simulated electromagnetic field（EF） distribution consolidated different effects of these three optical modes on resonant MOKE modulation. Such resonant polar MOKE possesses high sensitivity, which might pave the way to on-chip MO devices.

Microwave Magneto-Optic Bragg Modulators with Rectangular MSFVW Pulses

Microwave magneto-optic （MO） modulators can directly transform radio frequency （RF） signals into optical data through the Bragg diffraction of guided optical waves （GOWs） induced by microwave magneto-static waves （MSWs）. According to the MO coupled-mode theory, the modulation of continuous GOWs by a rectangular magneto-static-forwardvolume-wave （MSFVW） pulse in MO film waveguide is studied in the small signal case and the modulated optical pulse at the output is analyzed by means of an analytical form, which is dependent on the instantaneous diffraction intensity determined by the overlap of rectangular MSFVW pulse and light beam aperture. On the basis of it, the characteristics of MSFVW-based MO modulators can be explained well for the case of rectangular pulse modulation. It is also shown that the line codes of optical data generated by MO Bragg modulators can be controlled by adjusting the duty factor of modulating pulse signals.

Faraday rotations,ellipticity,and circular dichroism in magneto-optical spectrum of moire superlattices

We study the magneto-optical conductivity of a number of van der Waals heterostructures,namely,twisted bilayer graphene,AB–AB and AB–BA stacked twisted double bilayer graphene and monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride.As the magnetic field increases,the absorption spectrum exhibits a self-similar recursive pattern reflecting the fractal nature of the energy spectrum.Whilst twisted bilayer graphene displays only weak circular dichroism,the other four structures display strong circular dichroism with monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride being particularly pronounced owing to strong inversion symmetry breaking properties of the hexagonal boron nitride layer.As the left and right circularly polarized light interact with these structures differently,plane-polarized incident light undergoes a Faraday rotation and gains an ellipticity when transmitted.The size of the respective angles is on the order of a degree.

Investigation of ultracold atoms and molecules in a dark magneto-optical trap

In this paper, ultracold atoms and molecules in a dark magneto-optical trap （MOT） are studied via depumping the cesium cold atoms into the dark hyperfine ground state. The collision rate is reduced to 0.45 s-1 and the density of the atoms is increased to 5.6 × 1011 cm-3 when the fractional population of the atoms in the bright hyperfine ground state is as low as 0.15. The vibrational spectra of the ultracold cesium molecules are also studied in a standard MOT and in a dark MOT separately. The experimental results are analyzed by using the perturbative quantum approach.

Microwave-mediated magneto-optical trap for polar molecules

Realizing a molecular magneto-optical trap has been a dream for cold molecular physicists for a long time. However,due to the complex energy levels and the small effective Lande g-factor of the excited states, the traditional magneto-optical trap（MOT） scheme does not work very well for polar molecules. One way to overcome this problem is the switching MOT,which requires very fast switching of both the magnetic field and the laser polarizations. Switching laser polarizations is relatively easy, but fast switching of the magnetic field is experimentally challenging. Here we propose an alternative approach, the microwave-mediated MOT, which requires a slight change of the current experimental setup to solve the problem. We calculate the MOT force and compare it with the traditional MOT and the switching MOT scheme. The results show that we can operate a good MOT with this simple setup.

Study on Physical Process of Surface Oxidation of Rare Earth-Transition Metal Amorphous Magneto-Optical Thin Films

By using surface effects(Auger electron spectroscopy,X-ray photoelectron spectroscopy,polar Kerr effect)and volume effects(magnetization,torque curve)the physical process of surface oxidation of rare earth-transition metal amorphous magneto-optical thin films was studied in this paper.The rare earth elements oxidize preferentially and rich at the film surface,and the transition metals deplete in oxidation layer.Fe_2O_3 in the surface oxidation layer contributes to the planar magnetization,and thereby the anomalous peak appears near 180° on the torque curves and the amplitude of the peaks is related to the depth of surface oxidation layers.The iron bonds to oxygen easier than the cobolt.RE-Co magneto-optieal thin films have good properties of resistance to oxidation and humidity.

Surface Plasmon and Fabry-Perot Enhanced Magneto-Optical Kerr Effect in Graphene Microribbons

A single sheet of graphene exhibits the ability to turn polarization of light by several degrees in modest magnetic fields. Here we demonstrate that giant angle rotation in graphene in the terahertz range can be realized and further increased by the introduction of surface plasmon and constructive Fabry Perot interference with the supporting substrate. The maximum Kerr rotation angle is up to 15° in a single layer of graphene ribbons at 6 TPIz for the applied magnetic field 4 T. Such a magnification in magneto-optical Kerr effect can be realized in a fairly large incident angle.

基于熔盐堆尾气提取的99Mo生产评估

基于熔盐堆尾气提取99Mo同位素的生产方法引起了广泛的关注,但目前的工作局限于评估堆芯中99Mo的产量,对于其在整个回路中的迁移行为的关注不足。本文建立了一个熔盐堆中的贵金属迁移模型,并基于8 MW熔盐实验堆(Molten-Salt Reactor Experiment,MSRE)进行了贵金属分布验证,而后对MSRE尾气中99Mo粗产品的产量、比活度及运行状态的变化对生产的稳定性的影响进行了分析。结果表明,尾气中的99Mo有较高含量和比活度,移除率增加的工况对99Mo的比活度的影响是有益的,空泡比例及氧化还原电势变化的工况对99Mo的比活度影响不大,该方法可作为一种潜在的99Mo生产备选方案。

Mo添加对WC-Ni硬质合金微结构及性能的影响

采用X射线衍射(XRD)、扫描电子显微镜(SEM)和性能检测等方法研究了不同Mo添加量对WC-Ni-Mo硬质合金的WC粒度、硬度、摩擦磨损和耐腐蚀性能的影响。结果表明:在研究的成分范围内(w(Mo)=1.5%~2.0%),WC的平均晶粒尺寸基本不随Mo添加量的变化而变化;随Mo添加量的增加,WC-Ni-Mo硬质合金的硬度略微有所下降,而摩擦磨损性能得到提升。Mo质量分数为2%的WC-Ni-Mo硬质合金在酸性溶液中的耐腐蚀能力要高于Mo质量分数为1.5%的合金,并且具有更好的电化学稳定性。总体来看,WC-8.0%Ni-2.0%Mo合金的综合性能优于WC-8.5%Ni-1.5%Mo硬质合金。

Mo/Zr-SBA-15介孔分子筛吸附溶液中亚甲基蓝

采用一步水热晶化法将Zr掺杂到SBA-15骨架中制备了Zr-SBA-15,以Zr-SBA-15为载体,Mo为活性组分,制备了Mo/Zr-SBA-15吸附剂,对其进行了表征,并将Mo/Zr-SBA-15用于吸附溶液中的亚甲基蓝(MB),考察了Mo、Zr掺杂的SBA-15对MB的吸附性能。表征结果显示:Mo/Zr-SBA-15具有介孔结构,Zr进入SBA-15分子筛的骨架中,Mo部分负载至SBA-15的孔壁上,部分以MoO_(3)的形式均匀分散在SBA-15表面;随着Mo负载量的增加,Mo/Zr-SBA-15的比表面积与孔体积逐渐减小。实验结果表明:当Mo负载量(w)为10%时,对溶液中MB的吸附性能最佳;在MB质量浓度20 mg/L、Mo/Zr-SBA-15加入量0.2 g/L、初始溶液pH 5.9、温度25℃、吸附时间4 h的条件下,对MB的平衡吸附量达到90.3 mg/g;Freundlich模型能够更好地描述Mo/Zr-SBA-15对MB的吸附等温过程;25℃时,Mo/Zr-SBA-15对MB的饱和吸附量为173.3 mg/g;Mo/Zr-SBA-15经焙烧再生、循环使用4次后,平衡吸附量仅下降了7.6%,表现出良好的可再生性能。

医用同位素^(99)Mo吸附分离研究进展

医用同位素^(99)Mo是一种广泛应用于核医学领域的重要核素。由于常规的高浓缩铀裂变生产^(99)Mo的过程中存在安全隐患,人们已经开始寻找其他可靠的^(99)Mo生产途径。在分离^(99)Mo和^(99)mTc的方法中柱层析法具有很大优势,其中的关键是层析柱的材料,材料对^(99)Mo吸附能力关系到未来新一代^(99)Mo-^(99)mTc发生器的制备。本研究对医用同位素^(99)Mo的吸附分离进行综述,介绍^(99)Mo生产方式,^(99)Mo和^(99)mTc分离方法,以及目前对Mo具有一定吸附效果的吸附材料,为未来利用低比活度^(99)Mo吸附制备^(99)Mo-^(99)mTc发生器提供参考。

右江盆地大际山U-(Mo)矿床围岩蚀变特征及微量元素迁移规律——对区域内U、Au成生关系的指示

位于扬子地块西南缘的右江盆地,是全球第二大的卡林型Au矿(共伴生有Sb、Hg、Tl异常/矿化)矿集区,有着滇黔桂“金三角”的美誉。值得注意的是,该区除发育Au(-Sb-Hg-Tl)矿床外,还产有大量赋矿岩性和控矿构造相似的U矿床(点),成矿特色鲜明。前人对该区Au矿开展了大量研究,而U矿研究较少,对U、Au的成生关系尚不清楚。基于此,文章选取右江盆地内典型的U矿床——大际山U-(Mo)矿床为研究对象,通过开展岩矿相学研究和地球化学分析,厘定了矿化的围岩蚀变为硫化、沥青质化、磷铝锶石化、硅化和伊利石化,揭示了矿化过程中Re、Tl、Mo、U、Cd、Ni、Co、As、Sb、MREE的相对富集。蚀变矿物组合及元素迁移规律约束大际山U-(Mo)矿床中成矿物质可能来源于牛蹄塘组,成矿流体应为还原性有机流体与地表-近地表酸性、氧化性流体的混合,矿质沉淀发生在低温、酸性、还原环境中。综合分析认为,右江盆地内U、Au分布特征及矿床成因具有明显差异,二者应是不同成矿事件的产物。

Mo元素对13MnNiMoR钢焊缝微观组织及性能影响的研究

在制氢反应器运行过程中,焊缝质量和性能对设备的安全和稳定运行至关重要。文中以13MnNiMoR钢焊缝为研究对象,采用JMatPro软件仿真和试验相结合的研究方法,系统分析Mo元素对焊缝微观组织和力学性能的影响。研究结果表明:Mo元素的添加促进了M6C型碳化物的形成,抑制了M23C6型碳化物的析出,有利于材料的固溶强化和提高合金的强度。随着Mo含量的增加,焊缝区粒状渗碳体占比逐渐增加,且颗粒分布更加均匀,而焊缝的塑性和伸长率出现了下降。即:适量的Mo元素添加对于提升焊缝的硬度和抗拉强度是有益的,但过多的Mo元素会导致焊缝的塑性下降。

秘鲁Morococha斑岩-矽卡岩-浅成低温热液型矿床成矿地质特征与区域找矿方向

秘鲁中部Morococha地区位于中安第斯秘鲁中新世成矿带,是全球最具代表性的世界级斑岩-矽卡岩型和浅成低温热液型成矿系统之一。系统总结了该区斑岩型、矽卡岩型、浅成低温热液型等多种铜钼铅锌银多金属矿化成矿作用特征和最新的研究进展,结合区域岩浆-热液成矿作用过程,提出了下一步找矿方向。Morococha矿区位于秘鲁中部Yali穹隆北段,由中心部位的Toromocho斑岩型铜钼矿床及外围铅锌银金多金属矿脉组成。区内主要构造为北西向Morococha背斜,地层主要为二叠纪—三叠纪Mitu群火山碎屑岩、侏罗纪Pucara群碳酸盐岩、早白垩世Goyllarisquizga群海相碎屑岩和碳酸盐岩。矿区中新世岩浆活动主要为中中新世不含矿的闪长质侵入岩(14.3~14.1 Ma)和晚中新世与成矿有关的花岗闪长岩和长石斑岩岩株(9.4~7.7 Ma)。Morococha岩浆-热液系统(8.5~7.2 Ma)是其形成超大型斑岩型铜矿成矿的原因之一,铅锌银多金属矿化主要发生在斑岩型矿化之后约0.5 Ma,受区域构造控制。矿床在空间上显示出明显的金属分带特征,中心斑岩区域为富铜矿石,而远离斑岩区出现更多的富铅锌银矿石。秘鲁中部中新世成矿带分布着众多具有重要经济价值的脉状热液型铅锌银多金属矿床,总结近年来综合地质调查和研究成果,表明这些多金属矿床都属于斑岩-矽卡岩成矿系统的一部分,因此斑岩-矽卡岩型铜矿床及浅成低温热液型贵金属矿床是秘鲁中部重要的找矿方向。

Mo含量对激光熔覆CoCrFeNiW_(0.6)Mo_(x)高熵合金涂层组织与性能的影响

目的研究Mo含量的变化对激光熔覆CoCrFeNiW_(0.6)高熵合金涂层的影响。方法使用RFL-C1000光纤激光器,在45钢基体表面制备CoCrFeNiW_(0.6)Mo_(x)(x=0,0.2,0.4,0.6,0.8)高熵合金涂层,并利用Leica DVM6光学显微镜、扫描电镜(SEM)、X射线衍射仪(XRD)、能谱仪、显微硬度仪、电化学工作站对熔覆层的宏观形貌与稀释率、相结构、微观组织结构、硬度、耐腐蚀性能进行测试与分析。结果加入Mo元素后,结合状态与表面形貌良好,当x=0~0.4时,涂层微观组织主要呈树枝晶形态,且晶粒逐渐变细。当x≥0.6时,涂层表面开始有裂纹产生。随着Mo元素的添加,涂层逐渐析出σ相,晶粒尺寸逐渐减小。当x=0.8时,有共晶组织形成。涂层显微硬度随Mo元素的增加而增加,但由于x=0.8时出现较多裂纹,裂纹的出现影响了涂层硬度,导致x=0.8时的硬度减小。当x=0.6时,涂层平均显微硬度最高,达到了959.69HV0.3,约为CoCrFeNiW_(0.6)涂层平均硬度的20.32%。当x=0~0.6时,涂层耐腐蚀性能随着Mo元素含量的增加逐渐提升。当x=0.8时,耐腐蚀性能变差,其原因是裂纹的出现以及σ相的形成使得涂层耐腐蚀性变差。在x=0.6时,涂层耐腐蚀性能最好。结论Mo元素的加入使得涂层微观组织出现σ相,同时有细化晶粒的作用,可以显著改善涂层的硬度以及耐腐蚀性。

淬火温度对气瓶用Fe-Cr-Ni-Mo钢组织和力学性能的影响

为了优化一种气瓶用Fe-Cr-Ni-Mo钢的淬火工艺,采用SEM,TEM,EBSD和拉伸、冲击等观察和检测手段,研究了淬火温度对一种气瓶用Fe-Cr-Ni-Mo钢微观组织和力学性能的影响。结果表明,不同淬火温度处理后的合金钢,均呈现为板条马氏体组织,其碳化物析出和板条亚结构基本保持不变,而原始奥氏体晶粒则随淬火温度的提高而出现明显的粗化,由800℃的4.3µm长大到930,1200℃的29.6,371.1µm,同时有效晶粒尺寸(EGS)也逐渐增加,800,930,1200℃的EGS分别为0.60,1.20,3.22µm。淬火温度对合金钢的室温抗拉、屈服强度和断后伸长率影响较小,而随着淬火温度的提高,冲击吸收能量则出现了显著的下降,由800℃的119 J,下降到930,1200℃的68,38 J。EGS增大导致冲击断裂时出现解理断裂,是较高淬火温度合金钢冲击吸收能量下降的主要原因。淬火温度为800~860℃时,Fe-Cr-Ni-Mo钢具有良好的强韧性匹配,该研究结果对Fe-Cr-Ni-Mo钢制气瓶的工业化生产具有指导意义。