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Perpendicular magnetic tunnel junction and its application in magnetic random access memory

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Chinese Physics B 2014年第7期23卷 13-21页

作者：刘厚方 Syed Shahbaz Ali 韩秀峰 Beijing National Laboratory of condensed matter Physics institute of Physics Chinese Academy of Sciences

Recent progresses in magnetic tunnel junctions with perpendicular magnetic anisotropy （PMA） are reviewed and summarized. At first, the concept and source of perpendicular magnetic anisotropy （PMA） are introduced. Next, a historical overview of PMA materials as magnetic electrodes, such as the RE-TM alloys TbFeCo and GdFeCo, novel tetragonal manganese alloys Mn-Ga, L10-ordered （Co, Fe）/Pt alloy, multilayer film [Co, Fe, CoFe/Pt, Pd, Ni, AU]N, and ultra-thin magnetic metal/oxidized barrier is offered. The other part of the article focuses on the optimization and fabrication of CoFeB/MgO/CoFeB p-MTJs, which is thought to have high potential to meet the main demands for non-volatile magnetic random access memory.

关键词： magnetic random access memory perpendicular magnetic anisotropy spin transfer torque effect,magnetic tunnel junction

Synthesis and properties of Au-Fe_3O_4 and Ag-Fe_3O_4 heterodimeric nanoparticles

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Chinese Physics B 2010年第6期19卷 415-420页

作者：丁皓申承民惠超徐梽川李晨田园时雪钊高鸿钧 Beijing National Laboratory for condensed matter Physics Institute of PhysicsChinese Academy of Sciences

Monodisperse Au-Fe3O4 heterodimeric nanoparticles （NPs） were prepared by injecting precursors into a hot reaction solution. The size of Au and Fe3O4 particles can be controlled by changing the injection temperature. UVis spectra show that the surface plasma resonance band of Au-Fe3O4 heterodimeric NPs was evidently red-shifted compared with the resonance band of Au NPs of similar size. The as-prepared heterodimeric Au-Fe3O4 NPs exhibited superparamagnetic properties at room temperature. The Ag-Fe3O4 heterodimeric NPs were also prepared by this synthetic method simply using AgNO3 as precursor instead of HAuCl4. It is indicated that the reported method can be readily extended to the synthesis of other noble metal conjugated heterodimeric NPs.

关键词： heterodimeric structure monodisperse Au-Fe3O4 nanoparticles

Research trends in electron-doped cuprate superconductors

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Science China(Physics,Mechanics & Astronomy) 2015年第10期58卷 1-11页

作者： YUAN Jie HE Ge YANG Hua SHI YuJun ZHU BeiYi JIN Kui Beijing National Laboratory for condensed matter Physics Institute of Physics Chinese Academy of Sciences

In this review, we look back on some intriguing and puzzling issues in electron-doped cuprate superconductors, such as electron-hole asymmetry, two types of carriers, quantum critical points, order-parameter symmetry, etc. The necessity of study on this family is invoked in comparison with the hole-doped counterparts from several aspects. The related progress, especially in last few years, has been outlined point to point, as well as other hot topics like the discovery of ambipolar superconductors, the applications in superconducting electronics, and the emergency of superconductivity in parent compounds. In perspective, the utilization of blooming advanced techniques, electric double layer transistor and combinatorial film deposition, will bring some new insights into the mechanism such as electron-doped cuprate superconductors.

关键词： electron-doped electronic structure quantum critical phenomena

An intermediate state of T7 RNA polymerase provides another pathway of nucleotide selection

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Chinese Physics B 2017年第10期26卷 12-27页

作者：王展峰刘玉如王鹏业谢平 Key Laboratory of Soft matter Physics Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of Science

Phage T7 RNA polymerase is a single-subunit transcription enzyme, transcribing template DNA to RNA. Nucleoside triphosphate （NTP） selection and translocation are two critical steps of the transcription elongation. Here, using all-atom molecular dynamics simulations, we found that between pre- and post-translocation states of T7 RNA polymerase an intermediate state exists, where the O helix C-terminal residue tyrosine 639, which plays important roles in translocation, locates between its pre- and post-translocation positions and the side chain of the next template DNA nucleotide has moved into the active site. NTP selection in this intermediate state was studied, revealing that the selection in the intermediate state can be achieved relying on the effect of Watson-Crick interaction between NTP and template DNA nucleotide, effect of stability of the components near the active site such as the nascent DNA-RNA hybrid and role of tyrosine 639. This indicates that another NTP-selection pathway can also exist besides the main pathway where NTP selection begins at the post-translocation state upon the entry of NTE

关键词： RNA polymerase transcription elongation fidelity control molecular dynamics simulation

Synthesis and photoluminescence property of boron carbide nanowires

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Chinese Physics B 2008年第12期17卷 4585-4591页

作者：鲍丽宏李晨田园田继发惠超王兴军申承民高鸿钧 Beijing National Laboratory for condensed matter Physics Institute of Physics Chinese Academy of Sciences

Large scale, high density boron carbide nanowires have been synthesized by using an improved carbothermal reduction method with B/B203/C powder precursors under an argon flow at 1100℃. The boron carbide nanowires are 5-10 μm in length and 80-100 nm in diameter. Transmission electron microscopy （TEM） and selected area electron diffraction （SAED） characterizations show that the boron carbide nanowire has a B4C rhombohedral structure with good crystallization. The Raman spectrum of the as-grown boron carbide nanowires is consistent with that of a B4C structure consisting of B11C icosahedra and C-B-C chains. The room temperature photoluminescence spectrum of the boron carbide nanowires exhibits a visible range of emission centred at 638 nm.

关键词： carbothermal reduction vapour-liquid-solid (VLS) Raman photoluminescence

Brownian dynamics simulation of the cross-talking effect among modified histones on conformations of nucleosomes

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Chinese Physics B 2010年第4期19卷 461-468页

作者：段兆文李伟谢平窦硕星王鹏业 Key Laboratory of Soft matter Physics Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of Sciences

Using Brownian dynamics simulation, we studied the effect of histone modifications On conformations of an array of nucleosomes in a segment of chromatin. The simulation demonstrated that the segment of chromatin shows the dynamic behaviour that its conformation can switch between a state with nearly all of the histones being wrapped by DNA and a state with nearly all of the histones being unwrapped by DNA, thus involving the ＂cross-talking＂ interactions among the histones. Each state can stay for a sufficiently long time. These conformational states are essential for gene expression or gene silence. The simulation also shows that these conformational states can be inherited by the daughter DNAs during DNA replication, giving a theoretical explanation of the epigenetic phenomenon.

关键词： nucleosome histone modification DNA Brownian dynamics

Effective temperature and fluctuation-dissipation theorem in athermal granular systems:A review

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Chinese Physics B 2014年第7期23卷 73-78页

作者：陈琼厚美瑛 Key Laboratory of Soft matter Physics Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of Sciences

The definition and the previous measurements of a dynamics-relevant temperature-like quantity in granular media are reviewed for slow and fast particle systems. Especially, the validity of the fluctuation-dissipation theorem in such an athermal system is explored. Experimental evidences for the fluctuation-dissipation theorem relevant effect temperature support the athermal statistical mechanics, which has been widely explored in recent years by physicists. Difficulties encountered in defining temperature or establishing thermodynamics or statistical mechanics in non-equilibrium situations are discussed.

关键词： granular systems fluctuation-dissipation relation non-equilibrium thermodynamics

A-site ordered quadruple perovskite oxides AA'3B4O12

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Chinese Physics B 2016年第7期25卷 62-74页

作者：龙有文 Beijing National Laboratory for condensed matter Physics Institute of Physics Chinese Academy of Sciences Collaborative Innovation Center of Quantum matter

The A-site ordered perovskite oxides with chemical formula AA’BOdisplay many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La CuFeOand its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La MnCrOwith cubic perovskite structure. The Cu–Fe intermetallic charge transfer(LaCuFeO→ LaCuFeO) leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La MnCrOis a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.

关键词： high-pressure synthesis A-site ordered perovskite charge transfer multiferroicity

Frequency dependence of quantum path interference in non-collinear high-order harmonic generation

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Chinese Physics B 2016年第2期25卷 129-134页

作者：钟诗阳贺新奎滕浩叶蓬汪礼锋何鹏魏志义 Beijing National Laboratory for condensed matter Physics Institute of Physics Chinese Academy of Sciences

High-order harmonic generation（HHG） driven by two non-collinear beams including a fundamental and its weak second harmonic is numerically studied. The interference of harmonics from adjacent electron quantum paths is found to be dependent on the relative delay of the driving pulse, and the dependences are different for different harmonic *** frequency dependence of the interference is attributed to the spatial frequency chirp in the HHG beam resulting from the harmonic dipole phase, which in turn provides a potential way to gain an insight into the generation of high-order harmonics. As an example, the intensity dependent dipole phase coefficient α is retrieved from the interference fringe.

关键词： high harmonic generation non-collinear dipole phase ultrafast optics