磁性相互作用对合金析出相组织的影响

试验研究磁性相互作用对Bi-Mn合金中MnBi析出相磁致织构组织稳定性的影响 ,结果发现取向析出相晶粒间磁性相互作用不仅能够使织构组织在无磁场降温过程中稳定存在 ,而且能够使之在无磁场条件下重新加热至低于MnBi化合物Curie温度 (居里温度 ,指磁性相变发生的温度 )的固液两相区凝固过程中稳定存在。从磁性物理出发分析取向晶粒间磁性相互作用的特点 。

Role of Ni(NO_3)_2 in the preparation of a magnetic coal-based activated carbon

The role of Nil（NO3）2 in the preparation of a magnetic activated carbon is reported in this paper. Magnetic coal-based activated carbons （MCAC） were prepared from Taixi anthracite with low ash content in the presence of Ni（NO3）2. The MCAC materials were characterized by a vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, a scanning electric microscope （SEM）, and by N2 adsorption. The cylindri- cal precursors and derived char were also subjected to thermogravimetric analysis to compare their behavior of weight losses during carbonization. The results show that MCAC has a larger surface area （1074 m21g） and a higher pore volume （0.5792 cm3/g） with enhanced mesopore ratio （by about 10~）. It also has a high saturation magnetization （1.6749 emu/g） and low coercivity （43.26 Oe）, which allows the material to be magnetically separated. The MCAC is easily magnetized because the nickel salt is con- vetted into Ni during carbonization and activation. Metallic Ni has a strong magnetism on account of electrostatic interaction. Added Ni（NO3）2 catalyzes the carbonization and activation process by accelerat- ing burn off of the carbon, which contributes to the development of mesopores and macropores in the activated carbon.

Investigation on Magnetic Properties of Exchange Coupled Transition Metal Complexes──I. Application of the Kambe's Theory

Magnetic susceptibility of a series of dinuclear Ⅴ(Ⅳ) . Co(Ⅱ) and Mn(Ⅲ) complexes has been measured in the temperature range of 1. 5 ～300K. The isotropic Heisenberg theory has been applied to study the temperature-dependent behaviour of the magnetic susceptibility of these complexes and a corresponding program for fitting the experimental results has been set up on a VAX 11/785 computer. Conclusions can be drawn that the three complexes studied are all anti-ferromagnetically coupled with coupling constants -4. 4 , -115. 2 , and - 8. 4 cm￣(-1) for Ⅴ(Ⅳ) . Co(Ⅱ) ,and Mn(Ⅲ) complexes, respectively.

Analytical Study of Magnetohydrodynamic Propulsion Stability

In this paper an analytical solution for the stability of the fully developed flow drive in a magneto-hydro-dynamic pump with pulsating transverse Eletro-magnetic fields is presented. To do this, a theoretical model of the flow is developed and the analytical results are obtained for both the cylindrical and Cartesian configurations that are proper to use in the propulsion of marine vessels. The governing parabolic momentum PDEs are transformed into an ordinary differential equation using approximate velocity distribution. The numerical results are obtained and asymptotic analyses are built to discover the mathematical behavior of the solutions. The maximum velocity in a magneto-hydro-dynamic pump versus time for various values of the Stuart number, electro-magnetic interaction number, Reynolds number, aspect ratio, as well as the magnetic and electrical angular frequency and the shift of the phase angle is presented. Results show that for a high Stuart number there is a frequency limit for stability of the fluid flow in a certain direction of the flow. This stability frequency is dependent on the geometric parameters of a channel.

Magnetism of One-Dimensional Dipolar-Interaction Spin Chains with Perpendicular Anisotropy

We have investigated the magnetism of one-dimensional dipolar-interaction spin chains with perpendicular anisotropy by simulation. The behaviors of the magnetizations and the orientation correlations change dramatically as the anisotropy increases to the critical value. The domain length can be controlled by adjusting the temperature and the external field as well as the anisotropy. These properties are interesting and arise from the competition between the anisotropy and the interaction along the chain.

邻香草醛GdNi双核配合物磁学性质的密度泛函理论研究

基于密度泛函理论结合对称性破损态方法,选择不同的密度泛函方法和基组研究了以邻香草醛为主要配体的Gd~ⅢNi~Ⅱ双核配合物的磁学性质.结果表明,在TPSSh/TZVP(Gd为SARC-DKH-TZVP)水平下计算的磁耦合常数与实验值最吻合,能够准确描述配合物的磁学性质.磁轨道分析表明,顺磁中心Gd~Ⅲ和Ni~Ⅱ通过2个桥联氧原子O(3)和O(4)的超交换作用通道传递其铁磁性相互作用,其磁轨道由顺磁中心Gd~Ⅲ的4f_(z^3)轨道、桥联配体邻香草醛中酚氧原子的2p_y轨道、顺磁中心Ni~Ⅱ的3d_(z^2)轨道和3d_(xy)轨道组成.自旋布居分析显示,顺磁中心Gd~Ⅲ以自旋极化作用为主,顺磁中心Ni~Ⅱ以自旋离子作用为主,且Ni~Ⅱ离子的自旋离域作用对桥联配体的影响大于Gd~Ⅲ的自旋极化作用.

Hydrostatic pressure influence on magnetic phase diagram and structural parameters of SrTcO_3 from first-principles calculations

The effects of hydrostatic pressure of SrWeO3 are investigated by means of generalized gradient approximation （GGA） plus on-site Coulomb interaction corrections （GGA＋U） method within the framework of density functional theory （DFT）. Magnetic phase diagrams and structural parameters of SrTcO3 as a function of pressure are predicted. The magnetic ground state of SrTcO3 is found to keep in a G-type antiferromagnetic （G-AFM） structure under the pressure varying from 0 to 100 GPa. With the increase of the pressure, magnetic exchange energy increases, indicating a higher magnetic ordering temperature for SrTcO3 under a larger pressure. Besides the volume of the unit cell, lattice constants, and the bond length, the angles between typical Tc-O-Tc and Sr-O-Sr also decrease with the pressure, leading to strong structural distortions. Very obvious displace- ments of Sr and O atoms are observed under the pressure. Our work provides necessary understanding on electronic structures of SrTcO3 under high pressures.

Chiral cyanide-bridged 1D Fe~Ⅲ-Mn~Ⅲ heterobimetallic chains: Synthesis, structures and magnetic properties

Two couples of enantiomerically pure chiral cyano-bridged heterobimetallic one-dimensional (1D) chain complexes: [Mn((R,R)-Salphen)Fe(Tp)(CN)3],, (1) and [Mn((S,S)-Salphen)Te(Tp)(CN)3]n (2) (Salphen = N,N'-l,2-diphenylethylenebis (salicylideneiminato) dianion, Tp = tris(pyrazolyl) hydroborate), [Mn((R,R)-Salphen)Fe(Tp*)(CN)3·2H2O],, (3) and [Mn((S,S)-Salphen)Fe(Tp*)(CN)3.2H20],, (4) (Tp* = hydridotris (3,5-dimethylpyrazol-l-yl) borate), have been successfully synthesized by the reactions of MnⅢ schiff-base complexes with the tricyanometalate building block, [(Lxp)Fe(CN)3]- (Lyp = Tp or Tp*). All complexes are made up of neutral cyano-bridged zigzag double chains with (-Fe-CN-Mn-NC-),, as the repeating unit. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes. Magnetic studies demonstrate that ferromagnetic interactions are operative in these complexes. The ferromagnetic couplings become weak in the chains with the bending of the Mn-N=C angles.

Efficient removal of chlorophenols from water with a magnetic reduced graphene oxide composite

A magnetic reduced graphene oxide composite(MRGO) was successfully prepared by a simple and green method. MRGO was then used as an adsorbent and found to exhibit enhanced removal efficiency for various chlorophenols(CPs) from water compared with its precursors, graphene oxide(GO) and reduced graphene oxide. The CPs were o-chlorophenol, p-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. Among them, 2,4,6-trichlorophenol, which exhibited the lowest water solubility and highest molecular weight, most easily bound to MRGO. The preferential interactions between MRGO and CPs were hydrophobic interactions(?-? stacking and hydrophobic effect). This result was confirmed by the equilibrium adsorption behavior in which isotherms were all well described by Freudlich model, indicating heterogeneous and multilayer adsorption. Therefore, CP adsorption was more favored under neutral and acidic conditions, and the decreased removal efficiency of MRGO at higher p H levels was due to the improved hydrophilicity of CPs for deprotonation effect. Moreover, MRGO showed fast removal of each CP, achieving adsorption equilibrium within 10.0 min, presented efficient separation from water under an external magnetic field, and was easily regenerated using dilute Na OH aqueous solution after reaching saturated adsorption. Adsorption capacity of the regenerated MRGO had almost no loss until after five cycles. In summary, MRGO was an efficient adsorbent for the removal of various CPs and had considerable application potential in water treatment.

Di- and tetranuclear heterometallic CuⅡ-LnⅢ complexes (Ln = Gd and Dy): Synthesis, structure and magnetic properties

Four 3d-4f heterometallic complexes, [CuⅡ-LnⅢ(bpt)2(NO3)3(MeOH)] (Ln = Gd, 1; Dy, 2; bptH = 3,5-bis(pyrid-2-yl)-l,2,4- triazole), [CuⅡ-LnⅢ(μ-OH)2(bpt)4C14 (H2O)2]·6H2O (Ln = Gd, 3; Dy, 4), have been synthesized under solvothermal condi- tions. X-ray structural analyses reveal that 1 and 2 are isostructural while 3 and 4 are isostructural. In each complex, the copper and gadolinium or dysprosium ions are linked by two triazolate bridges and form a CuⅡ-LnⅢ dinuclear unit. The intramolecu- lar Cu-Ln distances are 4.542, 4.525, 4.545 and 4.538 ] for 1, 2, 3 and 4, respectively. Two dinuclear CuLn units are bridged by two OH- groups into the zig-zag tetranuclear {cunzLnm2} structures with the Ln(Ⅲ)...Ln(Ⅲ) distances of 3.742 and 3.684 for 3 and 4, respectively. Magnetic studies show that the antiferromagnetic CulI-Lnm interactions occur in 1 (Jcu = -0,21 cm-1) and 2. The antiferromagnetic interaction occurs in complex 3 with JcuGa = -0.82 cm-1 and JcdGd = --0.065 cm-1, while domi- nant ferromagnetic interaction occurs in complex 4.

Pressure-induced changes in the magnetic properties of the single crystal of Mn_3 single-molecule magnet

The magnetic measurements of the single crystal of Mn3 single-molecule magnet under high pressure at T=2 K have been performed.We find both the antiferromagnetic intermolecular coupling parameter J and the effective energy barrier to vary compared with the measurements at low pressure.The increase of|J|is estimated to be 12%at 0.7 GPa when compared with that of0 GPa,whereas the effective energy barrier becomes smaller with increasing pressure.Our results demonstrate that the intermolecular interaction of single-molecule magnet can be changed by pressure.Compared with the normal magnetic alloy,the effect of pressure on the magnetic properties of Mn3 is much more prominent,which implies that Mn3 may have great potential in magnetic multifunctional material.

Spin-canting and weak ferromagnetism in two novel 1D alternating chains with single cis-end-to-end azido bridges

By combining trans-4-styrylprydine （tsp） with azide system, we obtained two rare 1D cis-EE-azido-bridged compounds of [Mz（N3）4（tsp）4（H2O）2] [M = Mn （1）, Co （2）]. The magnetic study reveals that metal ions are anti-ferromagnetically coupled by cis-EE-azido-bridges and they show weak ferromagnetism below 4.0 K （1） and 4.2 K （2） due to the spin-canting caused by asymmetric magnetic interaction.

Low-field-induced spin-glass behavior and controllable anisotropy in nanoparticle assemblies at a liquid-air interface

Stacking nanoscale-building blocks into onedimensional(1D)assemblies with collective physical properties is a frontier in designing materials.However,the formation of 1D arrays using weak magnetic fields and an in-depth understanding of their magnetic properties remain challenging.Here,low-dimensional assemblies of iron oxide nanocubes with a disordered arrangement are fabricated at the diethylene-glycol/air interface in the presence of assembly fields(0/1/3/5/30/50 mT).Ring-shaped assemblies gradually transform as the assembly field increases from 0 to 50 mT,first to a porous network consisting of elongated assemblies and then to an aligned array of filaments,in which the aligned filaments are formed when the assembly field is≥3 mT and duration t>14 min.Spin-glass characteristics and static(dynamic)anisotropy factors~2(3)are achieved by tuning the strength of the assembly field.In the presence of a relatively weak assembly field,the interplay between dipolar interactions and disorder with respect to magnetic easy axis alignment leads to spin-glass characteristics.The alignment of the magnetic easy axes and the strength of the dipolar interactions increase with increasing assembly field,resulting in the disappearance of spin-glass characteristics and enhancement of the magnetic anisotropy.This study presents a strategy for obtaining magnetic assemblies with spin-glass behavior and controllable anisotropy while shedding light on the magnetic interactions of low-dimensional assemblies.

Modulational Instability of Spinor Condensates in an Optical Lattice

We obtain analytically the static states and corresponding collective-excitation spectra of a quasi-onedimensional spin-1 condensate modulated by a long-wavelength optical lattice in the weak lattice limit. It is demonstrated that both ferromagnetic and antiferromagnetic condensates may exhibit dynamical instability, which agree with the results with numerical simulation. In the homogeneous limit, our resuRs reduce to the previous results for homogeneous spinor condensates, i.e., dynamical instability can occur only for ferromagnetic interaction and an antiferromagnetic condensate is always dynamically stable.