铁磁性的物理本质

自发磁化和磁畴结构是铁磁性物质的两个基本特点。外斯(Weiss)"分子场"理论是解释自发磁化的经典理论,但并不能说明"分子场"的本质;根据量子力学研究认为"分子场"的本质是相邻原子中电子间的相互交换作用导致了磁有序,因此,从本质上说"分子场"属于静电作用。

Effect of NH_4^+ exchange on CuY catalyst for oxidative carbonylation of methanol

NaY and ion exchanged NaNH4Y zeolite with NH4NO3 were used as the support to prepare CuY cata‐lysts by a high temperature anhydrous interaction between the support and copper （II） acety‐lacetonate Cu（acac）2. The catalysts were used for the oxidative carbonylation of methanol to dime‐thyl carbonate （DMC） at atmospheric pressure. The textural and acidic properties of NaNH4Y zeolite and the CuY catalysts were investigated by X‐ray diffraction, scanning electron microscopy, N2 ad‐sorption‐desorption, temperature programmed reduction of H2, X‐ray photoelectron spectroscopy and temperature programmed desorption of NH3. With increasing NH4NO3 concentration, the NH4＋exchange degree increased while the crystallinity of the zeolite remained intact. Crystalline CuO was formed when the NH4＋exchange degree of NaNH4Y was low, and the corresponding CuY catalyst showed low catalytic activity. With increasing of the NH4＋exchange degree of NaNH4Y, the content of surface bound Cu＋active centers increased and the catalytic activity of the corresponding CuY catalyst also increased. The surface bound Cu＋content reached its maximum when the NH4＋ex‐change degree of NaNH4Y reached towards saturation. The CuY exhibited optimal catalytic activity with 267.3 mg/（g·h） space time yield of DMC, 6.9%conversion of methanol, 68.5%selectivity of DMC.

铁磁性物质的Weiss分子场及其本质

铁磁性物质的两个基本特点为自发磁化和磁畴结构。Weiss"分子场"理论是解释自发磁化的经典理论,却不能说明"分子场"的本质,量子力学研究认为"分子场"的本质是相邻原子中电子间的相互交换作用导致的磁有序,因此,"分子场"的本质是静电作用。

Characterization of coal using electron spin resonance： implications for the formation of inertinite macerals in the Witbank Coalfield, South Africa

Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experimental methods sensitive to the presence of radicals is electron spin resonance （ESR）, and differences in ESR spectra for different macerals may provide insight into coal-forming processes. In this study, ESR data along with the H/C atomic ratio （to infer the aromatic fraction） are used to characterize coal samples with the aim of assessing a fire-origin for dominant inertinite macerals. A medium rank C bituminous Witbank No. 4 Seam Upper coal （the parent） was density- fractionated to create vitrinite-rich and inertinite-rich samples. The parent sample consists of 42 vol% vitrinite and 49 vol% inertinite. The density-fractionated samples comprise of 81 vol% total vitrinite （dominated by collotelinite and collodetrinite）, and 63 vol% total inertinite （dominated by fusinite, semifusinite, and inertodetrinite）. The H/C ratio is 0.74 for the inertinite-rich sample, and 0.85 for the vitrinite-rich counterpart, suggesting the former sample is more aromatic. The ESR spectra obtained for the three samples were found to fit best using a Lorentzian distribution. The fit is noticeably better for the aromatic inertinite-rich sample, for which the spectrum is symmetric. This is attributed to pronounced electron mobility and exchange interactions. The higher radical content of the inertinite-rich and parent samples is attributed to the presence of specific inertinite macerals, namely： fusinite, semifusinite, and inertodetrinite. And, owing to the greater radical content of the inertinite-rich sample, the dominant inertinite macerals are interpreted to have formed through charring of plant matter.

Quantum Communication in Spin Chain with Multiple Spin Exchange Interaction

The transmission of quantum states in the anisotropic Heisenberg XXZ chain model with three-spin exchange interaction is studied. The average fidelity is used to evaluate the state transfer. It is found that quantum communication can be enhanced by the anisotropic coupling and multiple spin interaction. Such spin model can reduce the time required for the perfect state transmission where the fidelity is unity. The maximally entangled Bell states can be generated and separated from the whole quantum systems.

Spin-Polarization of Ferroelectric Supperlattice with Spin-1/2 Transverse Ising Model

By using the simple decoupling approximation to Fermi-type Green＇s function for the transverse Ising model under pseudospin theory, we systemically study the influence of different exchange interactions （transverse fields） of the two distinct materials on the polarization and Curie temperature of finite alternating superlattice. Meanwhile, we analyze the effect of the whole parameters of the top surface, present their influence on the polarization of each layer （including the mean polarization of the whole ferroeleetric superlattiee） and on the Curie temperature. The results show the ratio of the exchange interactions （the transverse fields）, which are of the two alternating materials have deeply impact on the polarization and Curie temperature of the supperlattice. Moreover, the top surface also has great influence on the whole ferroelectric superlattice.

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.

Monte Carlo Study of Planar Rotator Model with Weak Dzyaloshinsky-Moriya Interaction

With the help of an improvement Monte Carlo method, the Berezinskii-Kosterlitz-Thouless phase transition arising in two-dimensional planar rotator model with weak Dzyaloshinsky-Moriya （DM） interaction is investigated. The effects of the DM interaction on specific heat, susceptibility, and magnetization are simulated. The critical temperature of transitions is determined by the so-called Binder cumulant and the susceptibility of finite-size scaling. We find that the chiral Z2 symmetry reduced by the DM interactions plays an important role in a two-dimensional XY spin system, typically, the critical temperature is sensitive to weak DM spin couplings.

Transferring Multi-Dimensional Quantum States and Preparing Quantum Networks in Cavity QED

In this paper we propose a scheme for transferring quantum states and preparing quantum networks. Compared with the previous schemes, this scheme is more efficient, since three or four-dimensional quantum states can be transferred with a single step and information interchange of three-dimensional quantum states can be realized, which is a significant improvement. It is based on the resonant interaction of a three-mode cavity field with an atom. As a consequence, the interaction time is shortened greatly. Furthermore, we give some discussions about the feasibility of the scheme.

Properties of strangelets in a new quark mass confinement model with one-gluon-exchange interaction

The properties of strangelets at zero temperature with a new quark model that includes both the confinement and one-gluonexchange interactions is studied in a fully self-consistent method.The charge and parameter dependence of the stability of strangelets are discussed.It is found that the one-gluon-exchange interaction lowers the energy of a strangelet,and consequently allows the strangelet to be absolutely stable.The stable strangelet radius in the present model is smaller in comparison with the absence of one-gluon-exchange interaction,and can thus be much less than that of a normal nucleus with the same baryon number,according to the strength of the confinement and one-gluon-exchange interactions.

Luminescence properties of Eu^(2+) doped BaAl_2Si_2O_8 phosphor for white LEDs

The BaAl2Si2O8:Eu2+blue emitting phosphor was obtained through the one-step calcination process of precursors prepared bychemical co-precipitation method. The phase structure and luminescence propertied of the phosphor were investigated usingX-ray diffraction (XRD) and a fluorescence spectrophotometer. The excitation spectrum exhibited a broad band between 230nm and 400 nm and the emission peaking at about 470 nm was observed, which originated from the allowed f-d transition ofEu2+ions at Ba2+sites. Owing to the different optimal concentrations under different excitation wavelengths (254 nm and 365nm), the energy-transfer mechanism in this phosphor has changed from the dipole-dipole interaction to the exchange interac-tion of Eu2+ions.

A series of 3d-4f heterometallic frameworks comprising 2D lanthanide-organic layers and diverse Cu-complex pillars

Six novel 3D layer-pillared lanthanide-transition metal coordination polymers,LnCuX(IN)2(Ac)(H2O)(Ln = Tb,X = Br(1);Ln = Er,X = Cl(2)),[LnCuCl(IN)2(Ac)].H2O(Ln = Gd(3);Ln = Eu(4)),and [LnCu2Br2(IN)2(Ac)(H2O)].nH2O(Ln = Dy,n =0(5);Ln = Gd,n = 0.5(6))(IN = isonicotinate,Ac = acetate),have been obtained by linking Ln-organic layers and diverse Cu-complex pillars under hydrothermal conditions.1 and 2 are isostructural and formed by 2D Ln-IN-Ac layers and CuX(IN)2 pillars(X = Br(1),X= Cl(2));3 and 4 are isomorphic and comprised of 2D Ln-IN-Ac layers and dimeric Cu2Cl(IN)4 pillars;while 5 and 6 are isostructural and built from 2D Ln-IN-Ac layers and tetrameric Cu4Br4(IN)4 pillars.The magnetic susceptibility investigation of 3 and 6 shows the presence of weak antiferromagnetic exchange interactions between the Ln3+ ions.Compounds 1-6 represent good examples of using 2D Ln-organic layers and diverse Cu-complex pillars as building units to construct intriguing 3D Ln-TM-organic frameworks.

Electronic physics and possible superconductivity in layered orthorhombic cobalt oxychalcogenides

We suggest that cobalt-oxychalcogenide layers constructed by vertex sharing CoA_2O_2(A = S, Se, Te) tetrahedra, such as BaCoAO, are strongly correlated multi-orbitals electron systems that can provide important clues on the cause of unconventional superconductivity. Differing from cuprates and iron-based superconductors, these systems lack of the D_(4h) symmetry classification. However, their parental compounds possess antiferromagnetic(AFM) Mott insulating states through pure superexchange interactions and the low energy physics near Fermi surfaces upon doping is mainly attributed to the three t_(2g) orbitals that dominate the AFM interactions. We derive a low energy effective model for these systems and predict that a d-wave-like superconducting state with reasonable high transition temperature can emerge by suppressing the AFM ordering even if the pairing symmetry can not be classified by the rotational symmetry any more.

Color-Flavor Locked Strangelets in a New Quark Model with Linear Confinement and Coulomb-Type Interactions

The color-flavor locked(CFL) strangelets have been investigated in a new quark model with linear confinement and one-gluon-exchange interactions.Considering Coulomb energy,we have studied the properties of three kinds of CFL strangelets,namely,positively charged,negatively charged and nearly neutral CFL strangelets.It is found that the one-gluon-exchange effect lowers the energy of a strangelet considerably and thus makes it much more stable than without considering the effect.The charge of a positive strangelet is larger than 0.15A 2/3 with A being the baryon number,but smaller than that in bag model.The charge of a negatively charged or nearly neutral CFL strangelet is nearly proportional to A 1/3.

Metastability in the Spin-1 Blume–Emery–Griffiths Model within Constant Coupling Approximation

In this paper, the equilibrium properties of spin-1 Blume–Emery–Griffiths model are studied by using constant-coupling approximation. The dipolar and quadrupolar order parameters, the stable, metastable and unstable states and free energy of the model are investigated. The states are defined in terms of local minima of the free energy of system. The numerical calculations are presented for several values of exchange interactions on the simple cubic lattice with q = 6.

Interacting Theory of Chiral Bosons and Gauge Fields on Noncommutative Extended Minkowski Spacetime

Several interacting models of chiral bosons and gauge fields are investigated on the noncommutative extended Minkowski spacetime which was recently proposed from a new point of view of disposing noncommutativity.The models include the bosonized chiral Schwinger model,the generalized chiral Schwinger model (GCSM) and its gauge invariant formulation.We establish the Lagrangian theories of the models,and then derive the Hamilton's equations in accordance with the Dirac's method and solve the equations of motion,and further analyze the self-duality of the Lagrangian theories in terms of the parent action approach.

On the validity of microscopic calculations of double-quantum-dot spin qubits based on Fock-Darwin states

We consider two typical approximations that are used in the microscopic calculations of double-quantum dot spin qubits, namely,the Heitler-London(HL) and the Hund-Mulliken(HM) approximations, which use linear combinations of Fock-Darwin states to approximate the two-electron states under the double-well confinement potential. We compared these results to a case in which the solution to a one-dimensional Schr ¨odinger equation was exactly known and found that typical microscopic calculations based on Fock-Darwin states substantially underestimate the value of the exchange interaction, which is the key parameter that controls the quantum dot spin qubits. This underestimation originates from the lack of tunneling of Fock-Darwin states, which is accurate only in the case with a single potential well. Our results suggest that the accuracies of the current two-dimensional molecularorbit-theoretical calculations based on Fock-Darwin states should be revisited since underestimation could only deteriorate in dimensions that are higher than one.

The Role of α1(1260) in π^-p→α1^-(1260)p and π^-p → π^-ρ^0p Reactions Near Threshold

We report on a theoretical study of the π^-→α1（1260）p and π^-→π^-~0p reactions near threshold within an effective Lagrangian approach.The production process is described by t-channel ρ^0 meson exchange.For the π^-→π^-ρ~0p reaction,the final π^-p^0 results from the decay of the α1（1260） resonance,which is assumed as a dynamically generated state from the K＊ K and ρπ coupled channel interactions.We calculate the total cross section of the π^-→α1（1260）p reaction.It is shown that,with the coupling constant of the α1（1260） to ρπ channel obtained from the chiral unitary theory and a cut off parameter Δρ～1.5 GeV in the form factors,the experimental measurement can be reproduced.Furthermore,the total and differential cross sections of π^p→α1（1260）p→π^ρ^0p reaction are evaluated,and it is expected that our model calculations can be tested by future experiments.These reactions are important for the study of the α1（1260） resonance and would provide further constraints on the properties of the α1（1260） state.