材料期刊网

MAGNETIC PHASE DIAGRAM OF SmMn_2(Ge_(1-x)Si_x)_2 SYSTEM

Y.G. Wang , F.M Yang , C.P. Chen , N Tang , and Q.D. Wang (State Key Laboratory of Magnetism , Institute of Physics , Chinese Academy of Sciences , P.O. Box 603 , Beijing 100080 , China)(Department of Materials Science and Engineering , Zheiang University Hangzhou 310027 , China)

金属学报(英文版)

The magnetic phase diagram (x,T) of the SmMn2(Ge1-xSix)2 system has been studied by susceptibility and magnetization measurement. With increasing silicon concentration the temperature region of ferromagnetic ordering decreases on the phaae diagram.

关键词: magnetic phase diagram , null , null , null

Ab initio Studies on Magnetism of 3d Transition Metal Dimers

J.H. Gu , Z.L. Zhu , null , null , null , null

金属学报(英文版)

Ab initio calculations with the self-consistent full-potential linearized augmented-plane-wave method (FLAPW), under generalized gradient approximation, have been carried out to describe the electronic and magnetic properties of 3d transition metal dimers. It predicted the antiferromagneticity of Cr2 and ferromagneticity of other species. The Mn2 dimer was shown to be ferromagnetic coupling with a local magnetic moment of 5μB, retaining the value of its free atom state. The V2 and Ni2 exhibited low spin-polarization with local magnetic moment of only 1μB per atom. On the other hand, Fe2 and Co2 were highly spin-polarized with local magnetic moments of 3 and 2μB.

关键词: magnetism , null , null

Key R&D activities for development of new types of wrought magnesium alloys in China

Transactions of Nonferrous Metals Society of China

Many researchers in China are actively engaged in the development of new types of wrought magnesium alloys with low cost or with high-performances and novel plastic processing technologies. The research activities are funded primarily through four government-supported programs: the Key Technologies R&D Program of China, the National Basic Research Program of China, the National High-tech R&D Program of China, and the National Natural Science Foundation of China. The key R&D activities for the development of new wrought magnesium alloys in China are reviewed, and typical properties of some new alloys are summarized. More attentions are paid to high-strength wrought magnesium alloys and high-plasticity wrought magnesium alloys. Some novel plastic processing technologies, emerging in recent years, which aim to control deformation texture and to improve plasticity and formability especially at room temperature, are also introduced.

关键词: wrought magnesium alloy;microstructure;properties;alloy designing;plastic deformation;research projects;y-zr alloys;mechanical-properties;mg-4y-4sm-0.5zr alloy;grain-refinement;rare-earth;microstructure;gd;phase;temperature;evolution

From atom to monatomic wire: an ab initio study of magnetism in 3d transition metals

Zhili ZHU

金属学报(英文版)

A systematic ab initio study on magnetism of the 3d transition metals (TM) from atom to monoatomic wire within density functional theory with generalized gradient approximation (GGA) was performed. The results show that the spin coupling has strong intraatomic exchange strengths about 1 eV for isolated 3d TM atoms. The magnetic moments are distinctly lower than those of free atoms for all dimers except Mn₂. All the 3d TM elements exhibit magnetic ground states in the linear wire structure.

关键词: Ab initio study , Magnetism , Transition metal

Laboratory of Solid State Microstructures(LSSMS)

材料科学技术（英文）

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Exceptionally strong magnetism in the 4d perovskites RTcO(3) (R = Ca, Sr, Ba)

Physical Review B

The evolution of the magnetic ordering temperature of the 4d(3) perovskites RTcO(3) (R = Ca, Sr, Ba) and its relation with its electronic and structural properties has been studied by means of hybrid density functional theory and Monte Carlo simulations. When compared to the most widely studied 3d perovskites the large spatial extent of the 4d shells and their relatively strong hybridization with oxygen weaken the tendency to form Jahn-Teller like orbital ordering. This strengthens the superexchange interaction. The resulting insulating G-type antiferromagnetic ground state is characterized by large superexchange coupling constants (26-35 meV) and Neel temperatures (750-1200 K). These monotonically increase as a function of the R ionic radius due to the progressive enhancement of the volume and the associated decrease of the cooperative rotation of the TcO(6) octahedra.

关键词: total-energy calculations;augmented-wave method;basis-set;oxides

Statistical theory for hydrogen bonding fluid system of A(a)D(d) type (III): Equation of state and fluctuations

Science in China Series B-Chemistry

The equation of the state of the hydrogen bonding fluid system of A(a)D(d) type is studied by the principle of statistical mechanics. The influences of hydrogen bonds on the equation of state of the system are obtained based on the change in volume due to hydrogen bonds. Moreover, the number density fluctuations of both molecules and hydrogen bonds as well as their spatial correlation property are investigated. Furthermore, an equation describing relation between the number density correlation function of "molecules-hydrogen bonds" and that of molecules and hydrogen bonds is derived. As application, taking the van der Waals hydrogen bonding fluid as an example, we considered the effect of hydrogen bonds on its relevant statistical properties.

关键词: hydrogen bonding fluid;equation of state;fluctuation;correlation;effect;liquid methanol;temperature;water;dependence

Magnetotransport of Q1D Electrons Through Magnetic Barriers

Zhaoyang ZENG , Lide ZHANG , Xiaohong YAN

材料科学技术（英文）

Ballistic transport of Q1D electrons through multiple magnetic barriers is investigated. It is shown that ballistic conductance peaks disappear progressively with the increase of the oscillation frequency of the confining parabolic potential.

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THE APPARENT VISCOSITY OF SEMI-SOLID AZ91D ALLOY AT STEADY STATE

Z.S. Zhen , W.M. Mao , S.J. Yan

金属学报(英文版)

The Rheological behavior of semi-solid AZ91D at steady state is studied using a Couettetype viscometer in the present paper. The results show that the apparent viscosity ofsemi-solid AZ91D at the steady state increases with the solid fraction increasing, andgoes up sharply when the solid fraction reaches a certain value, which is called criticalfraction. In addition, the apparent viscosity of semi-solid AZ91D at the steady statetakes on a distinct downtrend with the shearing rate increasing, which indicates astrong shear thinning property. In addition, the critical solid fraction becomes higherunder larger shearing rate, owing to the more globular shape of the solid particles.Based on the present experiment results, an empirical equation is built as that, relatingthe steady state apparent viscosity of semi-solid AZ91D with the solid fraction fs andshearing rate γ at the same time: ηapp=10. 74exp(6.95fs)γ-0.86.

关键词: Rheological behavior , null , null , null , null

Two-step magnetization in a spin-chain system on the triangular lattice: Wang-Landau simulation

Physical Review B

The Wang-Landau algorithm is used to study the thermodynamic and magnetic properties of triangular spin-chain system based on two-dimensional Ising model in order to understand the magnetic-order dynamics in Ca(3)Co(2)O(6) compound. The calculated results demonstrate that the equilibrium state of the rigid spins produces the two-step magnetization curve at low temperature even when the random-exchange term is considered. This work indicates that the four-step magnetization behavior observed experimentally must be due to the nonequilibrium magnetization.

关键词: calcium compounds;exchange interactions (electron);Ising model;magnetisation;thermodynamics;one-dimensional ca3co2o6;density-of-states;compound ca3co2o6;phase-diagram;proteins;crystal