Au掺杂硅纳米线的稳定性和电子结构

采用基于密度泛函理论的第一性原理的方法,对Au掺杂[100]方向氧钝化硅纳米线(SiNWs)不同位置的形成能、能带结构、态密度及磁性进行了计算,考虑了Au占据硅纳米线的替代、四面体间隙和六角形间隙的不同位置.结果表明:Au偏爱硅纳米线中心的替代位置.Au掺杂后的硅纳米线引入了杂质能级,禁带宽度变窄.对于Au替代掺杂,杂质能级主要来源于Au的d、p态和Si的p态,由于Au的d态和Si的p态的耦合,Au掺杂硅纳米线具有铁磁性.对于间隙掺杂,杂质能级主要求源于Au的s态,是非磁性的.另外,根据原子轨道和电子填充模型分析了其电子结构和磁性.

山东省区域地球物理场

山东省各岩石磁性及密度参数基本可分为高、中、低 3类。山东省磁性结晶基底为泰山岩群、荆山群、胶东岩群、胶南岩群。以沂沭断裂带为界 ,山东省区域地球物理场分为鲁东区和鲁西区。鲁东区进一步划分为 3个次级区 ,即北部区、中部区和南部区。鲁西区进一步划分为 5个次级区 ,即鲁北重磁缓变区、鲁西南重高磁高区、中部弧形重磁场区、鲁西中部重低磁高区、鲁中南条带状重磁场区。各区地球物理场由于地质原因各具特点。山东省莫氏面总体呈东浅西深的缓变带 ,在该缓变带的背景上 ,呈周边地区条带状幔隆、中部幔坳的特征。山东省居里面呈近南北向带状分布 ,有德州聊城菏泽隆起带、滨州淄博滕州深坳带、蓬莱海阳千里岩响水隆起带。鲁中隆起北部碰撞带为山东省特殊的构造地带 ,其特征为侵入岩体沿该带断续出现、岩体围岩或岩体内铜及多金属矿化较为普遍、地热田沿该带时有分布、地形上为南部山区和北部平原的分界地带。胶莱盆地内 ,蓼兰—高密缺失莱阳群层位 ;中生代早期 ,盆地东北部与西南部是盆地的沉积中心 ,至晚期盆地中心北移 ,第三纪沉积中心则为平度蓼兰附近 ;盆地较深部位位于诸城凹陷、平度凹陷。胶莱盆地的次级构造单元可划分为 11个 ,七级镇构造带控制了胶莱盆地的成生和发展。

STUDIES ON MAGNETIC ABRASIVE MACHINING

This paper deals with the machining process using magnetic abrasives. Using an apparatus designed and made, a series of experiments are carried out, where the workpiece is cylindrical and the magnetic abrasives used are mainly Fe and Al 2O 3, for investigating the effects of machining time, working gap, rotating speed of workpieces, magnetic flux density on machining efficiency and surface roughness. At the end of this paper, the machining mechanism is also discussed.

MICROSTRUCTURE AND MAGNETISM OF Co/Ti and Co/Cu(Ni) MULTILAYERS

The multilayers in the forms of glass/Cu(Ni)(5.0 nm)/[Co(2.0 nm)/Cu(Ni)(0.5～3.7 nm)] 30 and glass/Ti(5.0 nm)/[Co(2.0 nm)/Ti(0.4～3.5 nm)] 30 ,prepared by dual facing target sputtering at room temperature,exhibit a soft magnetic property.The structural and magnetic properties of Co/Cu(Ni) and Co/Ti multilayers were examined as a function of the spacer layer thickness (d Ti and d Cu(Ni) ) by low angle X ray diffraction (LAXRD) and VSM measurements.The saturation magnetization M s of the Co/Ti multilayers was found to decrease with d Ti and approached to a constant value when d Ti was thick enough.But in the Co/Cu(Ni) multilayers,the M s was found to oscillate with d Cu(Ni) when d Cu(Ni) was less than 3.0 nm,and the oscillation period was about 1.0 nm.This arose from the different interlayer magnetic coupling effects.We interpret these two different kinds of interlayer magnetic couplings as the consequence of the competition between the RKKY like and superexchange couplings.

First Principles Study on FeAs Single Layers

FeAs^- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation （GGA） and GGA＋U. The calculated single-layer geometric and electronic structures are inconsistent with that of bulk materials. The bulk collinear antiferromagnetic ground state failed to be obtained in the FeAs^- single layer. The monotonous behavior of the Fe-As distance in z direction upon electron or hole doping is also in contrast with bulk materials. The results indicate that, in LaFeAsO and BaFe2As2, interactions between FeAs layer and other layers beyond simple charge doping are important, and a single FeAs layer may not represent a good model for Fe based superconducting materials.

DMRG Studies on Properties of Undoped and Doped Molecule-Based Ferromagnetic Chain

By using density matrix renormalization group （DMRG） method a model for organic molecule-based ferromagnetic chain is proposed. It is found that the ground states of Undoped and doped systems both exhibit ferrimagnetic ordering. The e-e repulsion plays an important role in the stability of the ferromagnetic state either in doped system or undoped system. For the undoped system, each unit cell coatains half of the total spins, which is consistent with Lieb＇s theorem. It is convinced that when the system is doped with one electron, a charge density wave is excited, which decreases the amplitude of spin density wave,therefore acting against the stability of ferromagnetic state.

重介悬浮液固相体积浓度的计算

根据重介悬浮液固相体积浓度的计算公式,并结合实例加以分析。正确地指导重介选煤生产。

Novel Implicit Lorentz Force-Type Magnetic Bearing for High-Precision Agile Maneuver of Magnetically Suspended Gyrowheel

The lorentz force-type magnetic bearing(LFTMB)with good linearity is suitable for the high-precision deflection control of the magnetically suspended gyrowheel(MSGW). Two kinds of novel implicit LFTMBs are proposed in allusion to the poor magnetic flux density uniformity of the existing explicit LFTMB. The improvement of uniformity is realized under the paramagnetic contribution of magnetic ring. Their structures are introduced,the mathematical models are established based on the equivalent magnetic circuit method and the magnetic fields are analyzed by the finite element method based on the design parameters. Simulation results indicate that the magnetic flux density uniformity of implicit LFTMBs is superior to the traditional explicit LFTMB. Furthermore,the implicit trapezoid LFTMB with double magnetic circuits is better than that of those with single magnetic circuit,in terms of the magnetic flux density uniformity and the magnetic flux density. The magnetic flux density of implicit trapezoid double magnetic circuits LFTMB is verified by the experiment. The error between the experimental results and the simulation results is within 5%,which shows that the implicit trapezoid double magnetic circuits LFTMB is promising to meet the high-precision agile maneuver requirement of the magnetically suspended gyrowheel.

Electronic Structure and Magnetic Properties of Cu[C(CN)_3]_2 and Mn[C(CN)_3]_2 Based on First Principles

The electronic structure and the magnetic properties of the molecule-based ferromagnets Cu[C（CN）3]2 and Mn[C（CN）3]2 are studied according to first principles within density-functional theory （DFT） and the full potential linearized augmented plane wave （FP-LAPW） method. The total energy, atomic spin magnetic moments, and density of states （DOS） of Cu[C（CN）3]2 and Mn[C（CN）3]2 are all calculated. The calculations reveal that the compounds have a stable ferromagnetic ground state and half-metallic properties. The total spin magnetic moment is 1.0μB for Cu[C（CN）3]2 and 5.0#B for Mn[C（CN）3]e per molecule, the magnetic moment mainly comes from metal atoms, although there is a slight contribution from N and C atoms.

Electronic and Magnetic Properties of Double Perovskite Ca_2CrSbO_6

First-principles calculations have been performed for the study of the electronic band structure and ferromagnetic properties of double perovskite Ca2CrSbO6. The density of states, total energy, spin magnetic moment, and charge density were calculated and analyzed in details. It is found that Ca2CrSbO6 has a stable ferromagnetic ground state and the spin magnetic moment per molecule is about 2.99#B. The chromium contributes the most in the total magnetic moments. The results indicate that Ca2CrSbO6 is half-metallic.

Magnetism and Sound Velocities of Iron Carbide （Fe3C） under Pressure

The elastic property and sound velocity of FeaC under high pressure are investigated by using the spin-polarized generalized gradient approximation within density-functional theory. It is found that the magnetic phase transition from the ground ferromagnetic （FM） state to the nonmagnetic （NM） state occurs at ～73 GPa. Based on the predicted Hugoniot of Fe3C, we calculate the sound velocities of FM-Fe3C and NM-Fe3C from elastic constants. Compared with pure iron, NM-FeaC provides a better match of compressional and shear sound velocities with the seismic data of the inner core, supporting carbon as one of the light elements in the inner core.

A Puzzle of Quantum Phase Transition on Gd-IMC by Tuning of Conduction Electron Concentration

Based on the critical unstable of both crystal and magnetic structure of Gd-intermetallic compound near the competition of two strongly independent subsystem （＂local 4f7＂ and ＂conduction electron concentration＂）, a new QPT （quantum point transition） is predicted by calculation of： （1） The band structure and density of state by density functional theory where a strong narrowing fluidity of fermions around EF with shifted to negative value ＂-0.8 eV ＂is observable in the Gd-intermetalliccompound system while in the Y-case, it is not dominated. An antiferromagnetic state on the fluidity of conduction band can be investigated; （2） The internal magnetic field due to short range exchange interaction Jij between the nearest neighbor of local magnetic moment of stable s-state of Gd （L = 0） through the mean field approximation and of Eigenvalue-Eigenfunction ~.（k） are calculated. While a strong negative value of Jy is predicted, the eigenvalue L（k） of the system shows a strong antiferromagnetic phase in the reciprocal lattice direction 〈010〉, 〈001〉 in the correlation length 3.38 ~A. Although the antiferromagnetic state at Rc 〈_ 3.38 °A is a puzzle but it is completely dominated at Rc = 9 °A after passing through the competition between ）.λmin（O） and λmin（π） in the ranger of 3.2 °A 〈 Rc 〈 9 °A. Since both of the antiferromagnetic subsystems are sensitive to the predicted KF, the effect of decreasing of conduction electron is proposed to investigate, the change of the antiferromagnetic ordering state to the competition of ferromagnetic state （in direction 〈010〉） and antiferromagnetic state （in direction 〈001 〉 and 〈 100〉） resulted to paramagnetic state in the long range Rc = 9 °A.

High densities of magnetic nanoparticles supported on graphene fabricated by atomic layer deposition and their use as efficient synergistic microwave absorbers

An atomic layer deposition （ALD） method has been employed to synthesize Fe3O4/graphene and Ni/graphene composites. The structure and microwave absorbing properties of the as-prepared composites are investigated. The surfaces of graphene are densely covered by Fe3O4 or Ni nanoparticles with a narrow size distribution, and the magnetic nanoparticles are well distributed on each graphene sheet without significant conglomeration or large vacancies. The coated graphene materials exhibit remarkably improved electromagnetic （EM） absorption properties compared to the pristine graphene. The optimal reflection loss （RL） reaches -46.4 dB at 15.6 GHz with a thickness of only 1.4 mm for the Fe3O4/graphene composites obtained by applying 100 cycles of Fe2O3 deposition followed by a hydrogen reduction. The enhanced absorption ability arises from the effective impedance matching, multiple interfacial polarization and increased magnetic loss from the added magnetic constituents. Moreover, compared with other recently reported materials, the composites have a lower filling ratio and smaller coating thickness resulting in significantly increased EM absorption properties. This demonstrates that nanoscale surface modification of magnetic particles on graphene by ALD is a very promising way to design lightweight and high-efficiency microwave absorbers.

Surface geometry and magnetism of Eu@C_(60) monolayer on Ag(111)

The surface geometry, electronic structure, and magnetism of Eu@C60 monolayer absorbed on Ag(111) have been investigated within the framework of density functional theory. The Eu@C60 monolayer has been constructed on Ag(111) substrate by one of the hexagon faces of C60 downward and its mirror plane face parallel to Ag(111). The Eu@C60 monolayer induces a recon- struction of the Ag(111) substrate and the perpendicular distance between the Eu@C60 and Ag(111) surface is 2.06 A, being shorter than that between C60 and Ag(lll) surface by 0.05A. There is no chemical bond formed between the Eu@C60 and Ag(111), and only 0.55e transferred from Ag(111) to Eu@C60. A large magnetic moment about 6.80/μB per unit cell is found for Eu@C60/Ag(111) system.

Ti Impurity Effect on the Optical Coefficients in 2D Cu_2Si: A DFT Study

The electronic and optical properties of 2D Cu_2Si and Cu_2Si:Ti are investigated based on the density functional theory(DFT) using the FP-LAPW method and GGA approximation. The 2D Cu_2Si has metallic and non magnetic properties, whereas adding Ti impurity to its structure changes the electronic behavior to the half-metallic with 3.256μB magnetic moment. The optical transition is not occurred in the infrared and visible area for the 2D Cu_2Si in x-direction and by adding Ti atom, the real part of dielectric function in the x-direction, Re(ε(ω))_x is reached to a Dirac peak at this energy range. Moreover, the absorption gap tends to zero in x-direction of the 2D Cu_2Si:Ti.

The first principles investigation of ferrite magnetic response with mismatch stress

The quasi-ferrite model is proposed and an appropriate PBE exchange functional with the spin density functional theory （SDFT） is selected for the calculation of the relation between magnetic moment and residual stress in ferrite using a quantum mechanics code. The relationship between ferrite magnetism and the carbon content is determined, and then a ferrite interstitial solid solution （ISS） model in a low carbon concentration state is replaced with an a-Fe model in the case of majority magnetic calculation. The band structure of the loaded α-Fe is compared with that of the unloaded a-Fe. The comparison shows that the energy of Fe atomic 3d orbital changes a little, while the energy of electron orbital of iron core below 3d almost keeps un- changed. The relationship between the magnetic moment and the stress appears intermittent due to the Bragg total reflection. The change in the magnetic moment due to lattice mismatch is much larger than that caused by mechanical loading.

Numerical and experimental study of magnetic fluid seal with large sealing gap and multiple magnetic sources

To improve the pressure capability of magnetic fluid seal with more than a 0.25 mm single edge gap,a magnetic fluid sealing structure with multiple magnetic sources which has five permanent magnets was designed.Magnetic field distributions under the pole pieces of the magnetic fluid seal with single and multiple magnetic sources were simulated by finite element method and its sealing pressure difference could be calculated according to the theoretical formula of the magnetic fluid seal.The effects of sealing gap height and magnetic source amount on the sealing capability were investigated experimentally.The theoretical and experimental results were compared,analyzed and discussed.The results demonstrated that the magnetic fluid seal with multiple magnetic sources was an effective method to improve the sealing capability for the rotary shaft with large gaps.The theoretical results agreed well with the experimental results when the height of the single edge gap was equal to 0.4 mm.However,it was found that when the height of the single edge gap was larger than 0.4 mm,the difference between the theoretical values and experimental values increased with the gap height because part of magnetic source had less or even no effect on magnetic fluid sealing capability.

Current-induced domain wall motion in magnetic nanowires with different dimensions

The current-driven domain wall motion was investigated on permalloy nanowires with different dimensions by micromagnetic simulations.The critical current density increased with the reduction in both the width and thickness of nanowires because of the enhanced hard-axis anisotropy.At a thickness of 5 nm,the critical current density decreased with the reduction of the nanowire width because of the reduced domain wall width.

Revealing interfacial space charge storage of Li^(+)/Na^(+)/K^(+)by operando magnetometry

Interfacial space charge storage between ionic and electronic conductor is a promising scheme to further improve energy and power density of alkali metal ion batteries(AMIBs).However,the general behavior of space charge storage in AMIBs has been less investigated experimentally,mostly due to the complicated electrochemical behavior and lack of proper characterization techniques.Here,we use operando magnetometry to verify that in FeSe_(2)AMIBs,abundant Li^(+)/Na^(+)/K^(+)(M^(+))can be stored at M_(2)Se phase while electrons accumulate at Fe nanoparticles,forming interfacial space charge layers.Magnetic and dynamics tests further demonstrate that with increasing ionic radius from Li^(+),Na^(+)to K^(+),the reaction kinetics can be hindered,resulting in limited Fe formation and reduced space charge storage capacity.This work lays solid foundation for studying the complex interfacial effect in electrochemical processes and designing advanced energy storage devices with substantial capacity and considerable power density.

On the Error Estimate of the Harmonic B_z Algorithm in MREIT from Noisy Magnetic Flux Field

Abstract Magnetic resonance electrical impedance tomography （MREIT, for short） is a new medical imaging technique developed recently to visualize the cross-section conduc- tivity of biologic tissues. A new MREIT image reconstruction method called harmonic Bz algorithm was proposed in 2002 with the measurement of Bz that is a single component of an induced magnetic flux density subject to an injection current. The key idea is to solve a nonlinear integral equation by some iteration process. This paper deals with the convergence analysis as well as the error estimate for noisy input data Bz, which is the practical situation for MREIT. By analyzing the iteration process containing the Laplacian operation on the input magnetic field rigorously, the authors give the error estimate for the iterative solution in terms of the noisy level 6 and the regularizing scheme for determining ABz approximately from the noisy input data. The regularizing scheme for computing the Laplacian from noisy input data is proposed with error analysis. Our results provide both the theoretical basis and the implementable scheme for evaluating the reconstruction accuracy using harmonic Bz algorithm with practical measurement data containing noise.