Lagrangian dynamics of polarized media with internal spin in general relativity

The complete system of field equations for a polarized medium with internal spin in interaction with an arbitrary set of fields is derived from a four-dimensional action integral. The general results are then specialized to the interaction with an Einstein-Maxwell field. The application to ideal spinning fluids is discussed.     

Quantum mechanical equations of motion of particles and spin in polarized media

Quantum mechanical equations of motion are obtained for particles and spin in media with polarized electrons in the presence of external fields. The motion of electrons and their spins is governed by the exchange interaction, while the motion of positrons and their spin is governed by the annihilation interaction. For particles with spin S ≥ 1, second-order terms in spin are taken into account. The equations obtained can be applied to describe the motion of particles and spin both in magnetic and nonmagnetic media.     

A spin polarized disc

We present a solution to the gravitational field equations in a Riemann-Cartan spacetime. The solution describes a disc of infinite radius and finite thickness. The solution has three forms which depend on the size of the acceleration. The matter content of the disc is a rotating spin fluid with a constant z acceleration and a spin density polarized along the axis of rotation. The fluid has zero axial and tangential pressures. There is a radial pressure. The energy density and pressure are finite within the disc.     

非均匀交换各向异性铁磁介质的非线性表面自旋波

利用Landau-Lifshitz 方程，研究了具有非均匀交换各向异性的半无限大铁磁体的非线性表 面自旋波理论。导出了部分钉扎纯交换铁磁介质的磁化强度所满足的边界条件和非线性表面 自旋波的色散关系，并获得了自旋波振幅沿z方向驻波的一维非线性Schrdinger方程和包 络振幅沿平面传播的二维非线性Schrdinger方程，结果表明铁磁体磁化强度的包络振幅随时空变化的性质是由二维非线性Schrdinger方程决定的。因此预言铁磁介质的表面非线性激发应是二维孤波的形式。对于弱非线性表面自旋波，对非线性Schrdinger方程存在孤子形式解的可能性作了讨论. 关键词： 表面自旋波 Landau-Lifshitz方程 非线性Schrdinger方程 孤子     

Simultaneous probing of exchange and spin-orbit interaction in spin polarized low energy electron diffraction from magnetic surfaces

An experimental set-up allowing simultaneous probing of exchange and spin-orbit scattering in spin polarized electron diffraction (SPLEED) from magnetic surfaces is described. In a theoretical analysis it is made clear why the measured scattering asymmetries are, in very good approximation, linear superpositions of the exchange and spin-orbit asymmetries. As an illustration SPLEED data for Ni (001) collected at various energies and angles of incidence of the primary beam, are presented and shown to be in good agreement with theoretical results.     

Development of a polarized ~3He neutron spin filter based on spin exchange optical pumping at China Mianyang Research Reactor

正Spin-polarized~3 He gas is widely used in many research areas.It is used to search for new spin-dependent interactions beyond the standard model[1,2].It works as a target for electron scattering when studying the spin structure of neurons in high-energy and nLuclear physics[3].Also,it works as a neutron spin filter(NSF)for polarizing/analyzing neutron polarizations in scattering experiments[4-7].One of the ad-     

Addition and spin exchange rate constants by longitudinal field μSR: The Mu+NO reaction

The addition reaction Mu+NO+M→MuNO+M and the spin exchange reaction Mu(↑) +MO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal field μSR at room temperature in the presence of up to 58 atm of N₂ as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λ_c) demostrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate constant has been determined ask _0,Mu =(1.10±0.25)×10⁻³² cm⁶ molecules⁻² s⁻¹, almost 4 times smaller than the corresponding H atom reactionk _0,H=3.90×10⁻³² cm⁶ molecules⁻² s⁻¹ [I.M. Campbell et al., J. Chem. Soc. Faraday Trans. 1.71 (1975) 2097]. The average value of the spin exchange rate constants in the 2.5–58 atm pressure range,k _SE=(3.16±0.06)×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, is in good agreement with previous values obtained by transverse field μSR [D.G. Fleming et al., J. Chem. Phys. 73 (1980) 2751].     

Analysis of spin polarized tunneling results

We report spin polarized tunneling results for Fe which confirm the original work of Tedrow et al. at MIT, and also use the data to illustrate an analysis which determines, with only qualitative reference to theoretical calculations, the true polarization index of the sample, provided the polarization is not too small.     

A spin polarized disc. II

We present a solution to the gravitational field equations which describes either a static disc in general relativity or a spin polarized rotating disc in a Riemann-Cartan spacetime. The disc has infinite radius and finite thickness. The energy and pressure are finite and positive within the disc and for some parameter choices, a radial fall off in the fluid parameters is possible. A comparison is made to axis-symmetric wall solutions.     

Energy behavior of spin electron cyclotron wave in a spin polarized plasma

In degenerate quantum plasma the energy behavior of electrostatic modes propagating perpendicular to the external magnetic field is studied by employing the separated spin evolution quantum hydrodynamic (SSE-QHD) model. This model reveals that spin electron cyclotron wave (SECW) appears additionally with the upper hybrid wave (UHW). In case of SECW, the curves for the energy flow speed at different levels of spin polarization effect flip over at a particular value of wave number. The spin polarization effect enhances the energy flow speed before this value of wave number and then suppresses it afterward. The energy flow speed is enhanced by spin polarization effect in the entire range of wave number for the propagation of UHW. The Bohm potential effect drastically increases the energy flow speed at high wave number domain in both the waves. This study may find its applications to understand the energy behavior inspin polarized solid state plasmas     

Spectrum of spin waves in cold polarized gases

The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically.     

Lagrangian dynamics of polarized media

The dynamical equations associated with polarized media in equilibrium are derived from a standard action. This approach applies to arbitrary thermodynamical models of the medium and provides a systematical method for the computation of the total energy-stress tensor for the coupled system of matter and fields.Fellow of the Schweizerischer Nationalfonds.     

伴随强光子辐射的自旋极化等离子体研究进展

强光子辐射导致的自旋极化等离子体是强激光与物质相互作用领域兴起的新研究方向。基于等离子体的自旋极化粒子束在固态材料诊断、原子核结构探测、弱电相互作用分析等方面具有广泛应用。同时,自旋作为电子的固有属性,它可为描述等离子体的行为状态提供新的信息自由度,因此自旋极化信号在强场等离子体自诊断也具有潜在应用。概述了在超强相对论等离子体中,由伽马光子辐射伴随的自旋翻转产生的自旋极化等离子体的物理机制,并对其在超高能量密度等离子体瞬态动力学反演的可能进行了介绍。     

Muon charge exchange and muonium spin exchange in gases

The spin dynamics of the positive muon undergoing cyclic charge exchange (μ⁺⇌Mu) while it is slowing down is compared with that in the case of repeated muonium spin exchange after thermalization. The expectation value of the spin polarization at timet aftern spin exchange collisions (att ₁,t ₂, ...,t _n ) are calculated explicitly from time dependent wave functions, and the quantity is averaged over the statistical distribution of the times of collisions and over all possible numbers of collisions betweent=0 and the observation timet. This result is complementary and equivalent to the conventional density matrix formalism, but offers an insight into the roles of spin flip and spin non-flip processes. The neutral fraction during slowing down is also discussed.     

Magnetism of surfaces by spin polarized photoemission

Spin polarized photoemission is used as a method to study the magnetic peoperties of solid surfaces. Here we consider those systems where the spin polarization is believed to be conserved during the photoemission process. The surface sensitivity of the experiment will be therefore mainly determined by the relative magnitudes of the escape depth of the photoelectrons and of the magnetic coherence length. We analyze both the temperature and magnetic-field dependence of the degree of spin polarizationP of the electrons emitted from single crystals of magnetite, Fe₃O₄, and thin films (D=2–3000 Å) of Fe, Co and Ni. These data yield information on 1) the temperature dependence of the magnetization of the surface, 2) the relative sizes of and, 3) changes of the magnetic moment of atoms in the surface layers, and 4) the surface magnetic anisotropy. We show that this technique emerges as a novel tool to study magnetic systems with free surfaces and to test the predictions of recent calculations of the magnetic properties of surfaces. Emphasis is given to the fact that only relative changes ofP and not its absolute values are relevant for an analysis of the data.     

Calculated optical curve for spin polarized MnO

A spin polarized band structure has been used to calculate the dielectric function of MnO. It appears thatd tod band transitions are at the origin of the absorption edge owing to thepd mixing. Like NiO, the onset excitations are ofpd charge transfer character. Only one metal ion is implied in the transfer process.