Low-temperature results of the statistical theory of noninteracting spin waves

Low-temperature predictions of a free-spin-wave theory that includes the correct spin-wave kinematics for theS=1/2, quantum Heisenberg ferromagnet, as described in a previous paper, are obtained for three dimensions using analytic and Monte Carlo techniques. The low-temperature propagator is found to be of boson form, and the low-temperature magnetization goes asT ^3/2, which agrees with the interacting theory at lowest order inT.     

A variational theory of fermion matter with spin dependent correlations

A variational wave function is constructed for a system of fermions interacting with a spin dependent potential. The correlations due to the repulsive core of the potential are described by a spin independent Jastrow product ansatz and the correlations due to the longer range part of the potential, which are assumed to be spin dependent, are described by an independent pair ansatz. A cluster expansion is derived for the variational energy and a set of hypernetted chain (HNC) equations obtained to sum the cluster series in terms of the elementary diagrams. Neglecting the elementary diagrams, the HNC equations are solved numerically for the spin dependent potential, V3, in neutron matter. The introduction of spin dependent correlations is found to give a small lowering of the variational energy in the HNC approximation. The results are very sensitive to an accurate treatment of the many-body terms within the HNC approximation, however, and it is shown that additional approximations can easily lead to an exaggeration of the effect of the spin dependent correlations.     

Temperature dependent linewidth of the conduction electron spin resonance in beryllium

A broadening in the low temperature CESR of beryllium is reported and possible mechanisms are discussed.     

Temperature series in the statistical theory of a crystal

A method of solving the Vlasov equation is developed for a crystal using an asymptotic expansion in terms of the temperature. The internal and free energy of cubic crystals is calculated with an accuracy up to terms proportional to T⁴.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 67–72, February, 1979.     

Raman cross section of spin ladders

We demonstrate that a two-triplet resonance strongly renormalizes the Raman spectrum of two-leg spin-ladders and moreover suggest this to be the origin of the asymmetry of the magnetic Raman continuum observed in CaV₂O₅. Received 25 April 2001 and Received in final form 9 May 2001     

Classical spin theory

Tensor and vector equations of motion of a classical charged particle with spin have been derived within the framework of the special theory of relativity on the basis of Frenkel's tensor. The anomalous magnetic moment of the particle is considered in a natural manner in deriving the equations. The expression for the forces acting on the particle is constructed with consideration of the effect of spin on the motion trajectory. The spin equations proved to coincide with those obtained previously by Nyborg and Good. The properties of these equations have been studied, and it has been shown that the various equations are in fact variant forms of one and the same equation. In the absence of an anomalous magnetic moment the tensor equation coincides with Frenkel's spin equation, and in the same situation the vector equation transforms to the equation obtained by Tamm. In the special case of homogeneous fields the vector equation coincides with the well-known Bargmann-Michel-Telegdi equation. In conclusion we present spin motion equations for a particle with electric and magnetic charges.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 67–76, February, 1980.     

Temperature dependent effects upon statistical particle and gamma ray emission from a compound nucleus

The temperature dependence of the nuclear level density parameter, a (T), is analyzed and the effects of this dependence upon the probabilities for statistical gamma-ray and neutron emission from a compound nucleus are studied. The competition between these decay channels, as a function of nuclear temperatures, is investigated. The results show a significant departure from the temperature independent, Fermi Gas Model approximation.     

Temperature dependent magnetic spin and orbital moments of mass-filtered cobalt clusters on Au(111)

Mass-filtered cobalt clusters with a size of 8 nm have been deposited in-situ under soft-landing conditions onto Au(111). The spin and orbital moments of the Co nanoparticles on a Au (111) single crystal have been investigated as a function of the temperature using the element-specific method of X-ray magnetic circular dichroism in photoabsorption. The results hint at an temperature-dependent spin-reorientation transition which is discussed with respect to different contribution to the magnetic anisotropy. Furthermore, by means of an in-situ oxidation experiment, the influence of an exposure to oxygen on the properties of the cobalt clusters has been investigated.     

Gluon condensate and spin dependent potentials

It is shown that a model in which the QCD vacuum is simulated by a stochastic background field leads to a potential whose spin dependent terms are in good agreement with phenomenology.     

The time dependent susceptibility of spin glasses

A relation is found between the time-dependent susceptibility of the Edwards-Anderson spin glass model and the spin self-correlation. The relation is explicitly proved to hold for Monte Carlo simulations of the model. The susceptibility peaks found in Monte Carlo calculations are discussed.     

Temperature dependent induced spin polarization in Cr2O3 overlayers on epitaxial CrO2 films

Spin-resolved inverse photoemission investigations show that the native Cr₂O₃ surface is antiferromagnetically coupled to the CrO₂ thin film substrate, with a temperature dependent induced polarization. The Cr₂O₃ exhibits the characteristic behavior of a rigid band/spin mixing behavior (non-Stoner) of a local moment paramagnet. The strong shifts of the conduction band edge from room temperature to low temperature suggests that the extent of the induced polarization of the Cr₂O₃ oxide surface, by the CrO₂ substrate, may be partly related to Coulomb blockade effects identified in CrO₂/Cr₂O₃/CrO₂ junctions.     

非平衡统计信息理论

阐述了以表述信息演化规律的信息（熵）演化方程为核心的非平 衡统计信息理论.推导出了 Shannon信息（熵）的非线性演化方程，引入了统计物理信息并 推导出了它的非线性演化方程.这两种信息（熵）演化方程一致表明：统计信息（熵）密度 随时间的变化率是由其在坐标空间（和态变量空间）的漂移、扩散和减损（产生）三者引起 的.由此方程出发，给出了统计信息减损率和统计熵产生率的简明公式、漂移信息流和扩散 信息流的表达式，证明了非平衡系统内的统计信息减损（或增加）率等于它的统计熵产生（ 或减少）率、信息扩散与信息减损同时 关键词： 统计信息（熵）演化方程 统计信息减损率 统计熵产 生率 信息（熵）流 信息（熵）扩散 动态互信息     

Dynamic statistical information theory

In recent years we extended Shannon static statistical information theory to dynamic processes and established a Shannon dynamic statistical information theory, whose core is the evolution law of dynamic entropy and dynamic information. We also proposed a corresponding Boltzmman dynamic statistical information theory. Based on the fact that the state variable evolution equation of respective dynamic systems, i.e. Fokker-Planck equation and Liouville diffusion equation can be regarded as their information symbol evolution equation, we derived the nonlinear evolution equations of Shannon dynamic entropy density and dynamic information density and the nonlinear evolution equations of Boltzmann dynamic entropy density and dynamic information density, that describe respectively the evolution law of dynamic entropy and dynamic information. The evolution equations of these two kinds of dynamic entropies and dynamic informations show in unison that the time rate of change of dynamic entropy densities is caused by their drift, diffusion and production in state variable space inside the systems and coordinate space in the transmission processes; and that the time rate of change of dynamic information densities originates from their drift, diffusion and dissipation in state variable space inside the systems and coordinate space in the transmission processes. Entropy and information have been combined with the state and its law of motion of the systems. Furthermore we presented the formulas of two kinds of entropy production rates and information dissipation rates, the expressions of two kinds of drift information flows and diffusion information flows. We proved that two kinds of information dissipation rates (or the decrease rates of the total information) were equal to their corresponding entropy production rates (or the increase rates of the total entropy) in the same dynamic system. We obtained the formulas of two kinds of dynamic mutual informations and dynamic channel capacities reflecting the dynamic dissipation characteristics in the transmission processes, which change into their maximum—the present static mutual information and static channel capacity under the limit case where the proportion of channel length to information transmission rate approaches to zero. All these unified and rigorous theoretical formulas and results are derived from the evolution equations of dynamic information and dynamic entropy without adding any extra assumption. In this review, we give an overview on the above main ideas, methods and results, and discuss the similarity and difference between two kinds of dynamic statistical information theories.     

Quantum statistical properties of photon-added spin coherent states

The photon-added spin coherent state as a new kind of coherent state has been defined by iterated actions of the proper raising operator on the ordinary spin coherent state. In this paper, the quantum statistical properties of photon-added spin coherent states such as photon number distribution, second-order correlation function and Wigner function are studied. It is found that the Wigner function shows the negativity in some regions and the second-order correlation function is less than unity. Therefore, the photon-added spin coherent state is a nonclassical state.     

Direct observation of spin dependent electronic structure of GaAs using spin polarized photoemission

The spectrum of spin plarization P(hv) of electrons photoemitted from negative electron affinity GaAs using circularly polarized light, 1.5 eV < hv < 3.6 eV, was measured by Mott scattering; it exhibits structure derived from the spin orbit split energy bands near Γ and L.     

Diagonalization-free implementation of spin relaxation theory for large spin systems

The Liouville space spin relaxation theory equations are reformulated in such a way as to avoid the computationally expensive Hamiltonian diagonalization step, replacing it by numerical evaluation of the integrals in the generalized cumulant expansion. The resulting algorithm is particularly useful in the cases where the static part of the Hamiltonian is dominated by interactions other than Zeeman (e.g. in quadrupolar resonance, low-field EPR and Spin Chemistry). When used together with state space restriction tools, the algorithm reported is capable of computing full relaxation superoperators for NMR systems with more than 15 spins.