3d spin dynamics and local moment of dilute Fe ions implanted into high Tc superconductors

The 3d spin dynamics and local susceptibility of isolated Fe ions recoil implanted into the high T_c superconductors YB₂Cu₃O_7−δ and EuBa₂Cu₃O_7−δ have been measured using the perturbed γ-ray distribution method. The observation of a Curie-type susceptibility and Korringa-type relaxation indicates a stable Fe moment in the superconductors with negligible orbital contributions. The observed 3d spin rate corresponds to an extremely small spin line-width of 0.5 meV at 300 K, which is consistent with a very weak coupling of the Fe spin to the host conduction electrons and with a weak pair breaking.     

Electromagnetic soliton-particle with spin and magnetic moment

Electromagnetic soliton-particle with both quasi-static and quick-oscillating wave parts is considered. Its mass, spin, charge, and magnetic moment appear naturally when the interaction with distant solitons is considered. The substantiation of Dirac equation for the wave part of the interacting soliton-particle is given.     

Neutrino induced magnetic moment and spin precession

When propagating through a dispersing medium, a massive neutrino acquires an induced magnetic moment that may give rise to a helicity flip in an external magnetic field with a larger probability than that caused by the anomalous magnetic moment. This phenomenon is investigated in the framework of relativistic quantum mechanics and of the generalized Bargmann–Michel–Telegdi equation.     

Effect of spin diffusion on the spin resonance in local moment systems

The effect of conduction electron spin diffusion on linewidth, lineshift and residue of the spin resonance in local moment systems is investigated. For the calculation of the transverse susceptibility a previously established kinetic equation approach is used. Low temperature Kondo-type anomalies of spin relaxation and diffusion are taken into account in the framework of Suhl's theory. The susceptibility exhibits considerable structure as a function of wavevector. In particular it is shown that the magnetic resonance bottleneck is broken for sufficiently large wavevectors. The effect of relaxation proceeding to local instead of total equilibrium is investigated and shown to introduce only minor modifications with one possible exception. Application of the theory to transmission electron spin resonance (TESR) is also discussed.     

Dirac-neutrino magnetic moment and the dynamics of a supernova explosion

The double conversion of neutrino chirality ν_L → ν_R → ν_L has been analyzed for supernova conditions, where the first stage is due to the interaction of the neutrino magnetic moment with plasma electrons and protons in the supernova core, and the second stage, due to the resonance spin flip of the neutrino in the magnetic field of the supernova envelope. It is shown that, in the presence of the neutrino magnetic moment in the range 10^?13 μ_B < μ_ν < 10^?12 μ_B and a magnetic field of ～10¹³ G between the neutrinosphere and the shock-stagnation region, an additional energy of about 10⁵¹ erg, which is sufficient for a supernova explosion, can be injected into this region during a typical shock-stagnation time.     

氢原子的磁矩--对自旋的讨论之一

利用氢原子的相对论性波动方程计算了氢原子的磁矩。结果表明,现行量子理论中所谓的总磁矩实际上都是由电子的轨道运动产生的,由此提出了所谓的总角动量实际上是相对论性轨道角动量的看法。     

Manipulating magnetic anisotropy and ultrafast spin dynamics of magnetic nanostructures

We present our extensive research into magnetic anisotropy. We tuned the terrace width of Si(111) substrate by a novel method: varying the direction of heating current and consequently manipulating the magnetic anisotropy of magnetic structures on the stepped substrate by decorating its atomic steps. Laser-induced ultrafast demagnetization of a Co Fe B/Mg O/Co Fe B magnetic tunneling junction was explored by the time-resolved magneto-optical Kerr effect(TRMOKE) for both the parallel state(P state) and the antiparallel state(AP state) of the magnetizations between two magnetic layers. It was observed that the demagnetization time is shorter and the magnitude of demagnetization is larger in the AP state than those in the P state. These behaviors are attributed to the ultrafast spin transfer between two Co Fe B layers via the tunneling of hot electrons through the Mg O barrier. Our observation indicates that ultrafast demagnetization can be engineered by the hot electron tunneling current. This opens the door to manipulate the ultrafast spin current in magnetic tunneling junctions. Furthermore, an all-optical TR-MOKE technique provides the flexibility for exploring the nonlinear magnetization dynamics in ferromagnetic materials, especially with metallic materials.     

Equilibrium values and dynamics of the net magnetic moment of a system of magnetic dipoles

Equilibrium states of different systems formed by coupled spherical bodies with dipole magnetic moments have been investigated using a numerical analysis. The bistable states and the corresponding values of the net magnetic moment are determined for a number of planar and three-dimensional systems of dipoles, and the conditions providing the existence of orientational configurations of coupled dipoles involved in the bistability are analyzed. The disturbances of the magnetic moment due to the quasi-static passage of an additional dipole and the dynamic modes excited by a homogeneous alternating magnetic field and represented by periodic, quasi-periodic, and chaotic oscillations of the magnetic moment of the system are considered for several types of systems. The bifurcation diagrams of the dynamic modes are constructed, and the specific features typical of the systems under consideration are revealed.     

Non-equilibrium dynamics in 3d spin glasses

The random spin structure of a quenched spin glass experiences a continuous re-structuring in the low-temperature spin glass phase; the spin glass ages. Some recent experimental studies of relaxation and temperature dependence of the low-frequency AC-susceptibility and DC-magnetisation have given essential new information on which are the governing physical parameters for the spontaneous re-construction of the spin configuration. These results are briefly reviewed and put into the context of a phenomenological real space picture of the spin glass phase. This picture includes: domains of spin glass ordered regions that use spontaneous droplet excitations as the only mechanism for their growth at constant temperature, chaos with temperature and overlap on short length scales between the equilibrium states at two different temperatures.     

Nonlinear dynamics of semiclassical spin in a time-dependent magnetic field

The dynamics of magnetic nanoclusters (or molecules) with a large spin in a magnetic field whose strength varies in proportion to time is analyzed. Such a field breaks the symmetry relative to rotations through 2π, as well as clockwise and counterclockwise rotations, and induces a number of new coherent quantum effects in the spin dynamics, such as the formation of a band energy spectrum with continuous spin states or the emergence of “Bloch” oscillations in spin precession and interband Zener tunneling. Bloch oscillations are manifested in experiment as equidistant identical jumps on the magnetization curve. The interband Zener tunneling gives rise to additional jumps and peaks on the susceptibility of the system.     

Equation for a particle with spin of 3/2 having anomolous magnetic moment

It is shown that it is possible to describe a particle with spin of 3/2 and anomolous magnetic moment within the theory of first-order relativistic wave equations in matrix form by introducing a minimum interaction with the external electromagnetic field. This is done by expanding the space of Lorentz group representations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 23–27, January, 1984.     

Temperature-induced local magnetic moment in narrow band electron systems

It is pointed out that the local spin fluctuations in certain exchange- enhanced paramagnetic metals can grow rapidly with temperature up to saturation, where the spin fluctuations may be regarded as arising from a set of local magnetic moments. Physical consequences of this phenomenon are discussed referring to experimental results.     

Asymptotics of 4d spin foam models

We study the asymptotic properties of four-simplex amplitudes for various four-dimensional spin foam models. We investigate the semi-classical limit of the Ooguri, Euclidean and Lorentzian EPRL models using coherent states for the boundary data. For some classes of geometrical boundary data, the asymptotic formulae are given, in all three cases, by simple functions of the Regge action for the four-simplex geometry.     

The spin and the anomalous magnetic moment of the electron in stochastic electrodynamics

It is proposed that the zitterbewegung induced on a harmonically bound electron by the zero-point radiation field accounts for the spin of the electron. Assuming that the measurement of a spin projection may be taken into account phenomenologically by considering the action of only the subensemble of the zero-point field with the corresponding circular polarization, the theory gives a satisfactory account of both the spin projection and the anomalous magnetic moment.