材料期刊网

THEORETICAL STUDY OF GIANT MAGNETO-IMPEDANCE IN AMORPHOUS FILMS WITH LONGITUDINAL MAGNETIC ANISOTROPY

J.Q. Yu , Y. Zhou , B.C. Cai and X.L. Zhao Information Storage Research Center , Research Lab of Thin Films and Microfabrication Technology , Shanghai Jiao Tong University , Shanghai 200030 , China

金属学报(英文版)

Giant magneto-impedance effect (MI) in thin films with longitudinal magnetic anisotropy is studied theoretically. The effective permeability of films as a function of external magnetic field Ha, anisotropy field and other parameters of films is presented using Landau - Lifshitz- Gilbert theory. The theoretical results agree well with experimental ones, which show a strong dependence of the impedance on the applied magnetic field.

关键词: magneto-impedance effect , null , null , null

Research progress of electrochemical hydrogen storage in carbon nanotubes

新型炭材料

The uptake of hydrogen in carbon nanotubes is a hot topic in carbon nanotube research. Currently there are two methods to store hydrogen in carbon nanotubes. One is based on gas phase hydrogen storage and the other is based on an electrochemical method. Fundamental principles, theoretical calculations, and the interaction between hydrogen and carbon nanotubes for electrochemical hydrogen storage are reviewed. In particular, an overview of the most recent progress on electrochemical hydrogen storage in both single-walled carbon nanotubes and multi-walled carbon nanotubes is given and the prospect of their use in high performance batteries is highlighted.

关键词: carbon nanotubes;electrochemistry;gas storage;nanofibers;adsorption

Spin Hamiltonian parameters and defect structure for the X-ray-induced NbLi4+ center in LiNbO3 crystal

Journal of Alloys and Compounds

The spin Hamiltonian (SH) parameters (g factors g(x), g(y), g(z) and hyperfine structure constants A(x), A(y), A(z)) of the low-symmetry Nb-Li(4+) antisite defect center in the X-ray-irradiated congruent undoped LiNbO3 crystal are calculated from the high-order perturbation formulas of SH parameters for d(1) ions. The calculated results are in reasonable agreement with the experimental values. Some information related to the defect structure of the Nb-Li(4+) center (characterized mainly by the Nb-Li(4+) displacement Delta z from the ideal Li+ site along C-3 axis and the displacement Delta x of O2- ions in the oxygen triangle between Nb-Li(4+) and Nb-Nb(5+)) is obtained from the calculations. These displacements are consistent with the expectation based on the electrostatic interaction and electron cloud overlap. The results are discussed. (C) 2006 Elsevier B.V. All rights reserved.

关键词: ferroelectrics;inorganic compounds;crystal and ligand fields;point;defect;electron paramagnetic resonance (EPR);temperature-dependence;lithium-niobate;epr parameters;cr3+ centers;endor;ions;ruby

Re-interpretation of EPR spin-Hamiltonian parameters b(2)(m) for Gd3+-O2- center in the tetragonal phase of perovskite-type compound Rb1-xKxCaF3 with x=0.05

Physica Status Solidi B-Basic Research

The spin-Hamiltonian parameters b(2)(2), b(2)(-1) and b(2)(0) for Gd3+-O2- center in the tetragonal phase of Rb0.95K0.05CaF3 perovskite-type compound are studied by the superposition model which considers the (GdOF5)(4-) octahedron distortion related to the elongation or release of the metal-ligand bond lengths in the octahedron. The parameters b(2)(m) can be reasonably explained, and information for the local phase transition behaviour is obtained.

关键词: transitions;disorder;crystals;resonance;rbcaf3;rbcdf3

Study of properties of mixed ferro-ferrimagnetic ising compounds with (A(x)B(1-x))(y)C

Communications in Theoretical Physics

The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(x)B(1-x))(y)C-z where A(z) B-z and C are three different magnetic ions and form three different sublattices, are studied by using the standard mean-field theory. The phase diagram which is related to experimental work of molecule-based ferro-ferrimagnet ((NixMn1-xII)-Mn-II)(1.5)[Cr-III(CN)(6)].zH(2)O is obtained. The magnetization curves(z) internal energy(z) and specific heat of the same mixed (A(x)B(1-x))(y)C system are also investigated.

关键词: mixed ferro-ferrimagnet;Ising model;phase diagram;internal energy;specific heat;mean-field analysis;magnetic-properties;prussian blue;alloy

承钢公司成功试炼X70、C700L两钢种

钢铁

近日，承钢公司试炼管线钢X70、卷板C700L获成功，钢坯成分、气体含量、铸坯质量等指标均达到标准要求。管线钢X70是具有高强度、高韧性和良好焊接性能的高级别管线。提钒钢轧二厂在总结以往管线钢生产经验的基础上，于4月15日对X70钢组织试制，

关键词: X70 , 钢种 , 试炼 , 管线钢 , 气体含量 , 铸坯质量 , 焊接性能 , 生产经验

Investigations of the g factors for the orthorhombic Co2+ center in YBa2Cu2.7Co0.3O7-x at room temperature

Physica C-Superconductivity and Its Applications

The anisotropic g factors g(x), g(y) and g(z) for the orthorhombic Co2+ center on the Cu(l) site in YBa2Cu2.7CO0.3O7-x at room temperature are theoretically investigated from the perturbation formulae of the g factors for a 3d(7) ion having low spin (S = 1/2) under octahedra with orthorhombic distortion. In these formulae, the contributions to the g factors from the orthorhombic crystal-fields as well as the ligand orbitals and spin-orbit coupling are taken into account based on the cluster approach. This center may be attributed to Co2+ located in a moderately compressed oxygen octahedron with additional orthorhombic distortion. The significant decline (characterized by the reduction factor y approximate to 0.13) of the energy separations due to the Jahn-Teller effect is suggested, by analyzing the experimental g factors. The calculated g factors based on the above contributions show good agreement with the observed values. In addition, the pronounced decrease in the intensity and the remarkable nonlinear increase in the g, of Co2+ EPR spectra as the temperature is lowered from room temperature to 150 K are also mentioned, in view of the opening of the spin gap due to antiferromagnetic interactions. (c) 2007 Elsevier B.V. All rights reserved.

关键词: electron paramagnetic resonance;crystal fields and spin hamiltonians;Co2+;YBa2Cu2.7Co0.3O7-x;atomic screening constants;d-orbital theory;paramagnetic-resonance;scf functions;spin gap;field;ions;0-less-than-or-equal-to-x-less-than-or-equal-to-0.30;yba2cu3o7-delta;la2-xsrxcuo4

Investigation of the EPR g factors and defect structure for the Cu2+-V-Na center in the X-irradiated NaCl: Cu+ crystal

Physica B-Condensed Matter

The g factors of a tetragonally-compressed Cu2+ center in NaCl: Cu+ crystal X-irradiated at room temperature are calculated from the high-order perturbation formulas based on the two-mechanism model. In the model, the contribution to g factors from both crystal-field (CF) and charge-transfer (CT) mechanisms are included. The calculations are based on the defect model that the tetragonally-compressed Cu(2+)center is assigned to the Cu2+ ion (which is caused by Cu+ ion (at the Na+ site) irradiated by X-ray) associated with a nearest Na+ ion vacancy V-Na along C-4 axis due to charge compensation. From the calculations, the g factors g(parallel to) and g(perpendicular to) are explained and the defect structure (charactering by the displacement Delta Z of the Cl- ion intervening in Cu2+ and V-Na) of the Cu2+ (or Cu2+-V-Na) center is obtained. The results are discussed. (C) 2011 Elsevier B.V. All rights reserved.

关键词: Electron paramagnetic resonance (EPR);Defect structure;Crystal- and;ligand-field theory;NaCl;Cu2+;spin-hamiltonian parameters;jahn-teller;single-crystals;cu2+;ions;resonance;spectrum;ligand;temperature;transitions

Study on hydrogen storage properties of LaNi(3.8)Al(1.2-x)Mn(x) alloys

International Journal of Hydrogen Energy

Effects of the Mn substitution on microstructures and hydrogen absorption/desorption properties of LaNi(3 8)Al(1 2-x)Mn(x) (x = 0 2 0 4 0 6) hydrogen storage alloys were investigated The pressure composition (PC) isotherms and absorption kinetics were measured in a temperature range of 433 K <= T <= 473 K by the volumetric method XRD analyses showed that with the increase of the Mn content in the LaNi(3 8)Al(1 2-x)Mn(x) alloys the lattice parameter a was decreased c increased and the unit cell volume V reduced It was found that the absorption/desorption plateau pressure was increased and the hydrogen storage capacity was enhanced with the increase of Mn content The absorption/desorption plateau pressure of the alloys was linearly changed with the Mn content x and the lattice parameter a while the hydrogen storage capacity was linearly increased with the increase of c/a ratio It was also found that the slope factor S(f) was closely correlated with the lattice strain of the alloys (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved

关键词: Metal hydride (A);Hydrogen absorbing materials (A);Gas solid reactions;(B);Thermodynamic properties (C);structural-properties;sorption properties;system;hydrides;lani5-xalx;ni

Multi-state resistive switching memory with secure information storage in Au/BiFe0.95Mn0.05O3/La5/8Ca3/8MnO3 heterostructure

Applied Physics Letters

The ferroelectric polarization dependent bipolar and conductive filament related unipolar resistive switching behaviors are investigated systematically in Au/BiFe0.95Mn0.05O3/La5/8Ca3/8MnO3 heterostructure. The results show that after conductive filaments are formed, the ferroelectric state previously polarized will keep almost unchanged. By combining the two resistive switching mechanisms together under appropriate programming conditions, a tri-state-like resistive switching behavior is realized, finding effective routes in designing high-density storage. According to these distinctive characteristics, a prototype memory device with secure information storage is properly designed as an example of promising applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4714514]

关键词: thin-films