Nonlinear surface magnetic polaritons in a nonuniform magnetic field

High-frequency surface magnetic polaritons of finite amplitude propagating along the interface between a ferrite and a nonlinear insulator in a weakly nonuniform, shaft-shaped external magnetic field are investigated theoretically. The analysis is based on employment of the variational method together with bilinear relations having the form of Lorentz’s lemma. It is shown that the wave dispersion and the transverse profile of a wave along the field nonuniformity depend significantly on the amplitude of the wave. Zh. Tekh. Fiz. 68, 92–95 (September 1998)     

Nonlinear Kerr effect in magnetic crystals

The reflection of an intense light wave from the boundary of a semiinfinite magnetic crystal is investigated theoretically. Expressions are obtained for the rotation angle of the polarization ellipse and the degree of ellipticity of the reflected wave as a function of the polarization of the incident radiation. The physical wave-interaction mechanisms that give rise to this effect are established. Fiz. Tverd. Tela (St. Petersburg) 41, 656–659 (April 1999)     

A quantitative determination of magnetic fluctuations in CuGeO3

A polarised neutron scattering investigation has been carried out on a powder sample of CuGeO₃ within the temperature range of 1.5 K to 600 K. The magnetic scattering has been separated from all other contributions by using polarised neutrons and polarisation analysis and placed onto an absolute scale. At low temperatures the long wavelength components of the paramagnetic response are suppressed consistent with the formation of Cu dimers in which the magnetic moments are correlated antiferromagnetically. This form of the scattering persists to temperatures well above the dimerisation temperature T _sp ∼ 14 K. However as the temperature is raised the intensity of the long wavelength spin fluctuations increases and above ∼150 K they are the dominant feature in the wave vector dependence of the response. At all temperatures the observed scattering extrapolates smoothly to the Q = 0 value given by the uniform susceptibility. Consequently the thermal variation of the uniform susceptibility arises from the evolution of the long wavelength magnetic fluctuations. At large wave vectors the energy dependence of the scattering revealed that the response occurs below 16 meV in agreement with the reported maximum magnetic excitation energy at the zone boundary in the ground state. However the total magnetic scattering is significantly less than that expected for a local moment system suggesting that the spectrum of thermal and quantum fluctuations overlap. Received 30 May 2000 and Received in final form 22 March 2001     

Anisotropic momentum transfer in low-dimensional electron systems in a magnetic field

In low-dimensional systems with an asymmetric quantizing potential, an asymmetric electron energy spectrum ε(p)≠ε(−p), where p is the electron momentum, arises in the presence of a magnetic field. A consequence of such an energy spectrum is that momentum transfer to the electron system in mutually opposite directions in the presence of an external perturbation is different. Therefore, in the presence of a standing electromagnetic wave momentum is transferred from the wave to the electrons, which gives rise to a new type of electromotive force. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 551–555 (25 October 1997)     

A full wave model of high-harmonic EMIC wave propagation in sheared magnetic fields

ABSTRACT

A new dispersion relation, with finite Larmor orbit effects, for oblique propagating electromagnetic ion cyclotron (EMIC) waves in a magnetized plasma medium, is derived including the magnetic shear effect. The approximate, yet accurate, dispersion relation is used to implement the ray tracing model. A parabolic magnetic field is considered to model the geomagnetic field in the magnetosphere. Energetic protons are also considered as resonant particles. The propagation characteristics of EMIC waves in the vicinity of the ion cyclotron resonances are investigated in some detail. The results reveal adiabatic oscillating motion for wave and magnetic field fluctuations where high harmonics limit the wave damping and confines the magnetic fluctuations. For inward propagating EMIC waves we find (1) turning points which depend on the wave launch position, and (2) wave trapped areas playing a role in quasi-coherent wave-particle interaction in agreement with the observational and theoretical studies. This wave trapping is an effective process for particle acceleration in the context of space plasmas.     

Effect of phasons and magnetic fields on the electronic spectrum of a three-dimensional quasicrystal

The effect of phasons and magnetic fields on the electronic spectrum of an icosahedral quasicrystal is investigated in the tight-binding approximation. Phasons smooth the singular spectrum and produce a greater delocalization of the critical wave functions. A magnetic field shifts the limits of the spectrum, smooths the spectrum, lifts the degeneracy, and also delocalizes the wave functions. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 9, 659–661 (10 May 1999)     

Nuclear magnetic shielding of a hydrogen atom in (1) an electric field-gradient and (2) a cage

The ground state wave function of a hydrogen atom in an electric field-gradient F' is obtained, correct to the first power in F', and the nuclear magnetic screening constant σ evaluated. The F' contribution to σ vanishes if all directions of F' relative to the applied magnetic field are equally probable. In part (2), the influence of a uniform compression of the H-atom on σ is examined. This effect, which will predominate at sufficiently high pressures, causes a decrease in the electronic polarizability but an increase in σ.     

Energy spectra and quantum crystallization in two-electron quantum dots in a magnetic field

Quantum crystallization of electrons in a quantum dot (QD) subjected to an external magnetic field is considered. Two-electron QDs with two-dimensional (2D) parabolic confining potential in an external transverse magnetic field are calculated. The Hamiltonian is numerically diagonalized in the basis of one-particle functions to find the energy spectra and wave functions for the relative motion of electrons with inclusion of electron-electron interaction for a broad range of the confining-potential steepness (α) and external magnetic fields (B). The region of the external parameters (α, B) within which a gradual transition to quantum crystalline order occurs is numerically determined. In contrast to a 2D unbounded system, a magnetic field acts nonmonotonically on “crystallization” in a quantum dot with several electrons because of a competition between two effects taking place with increasing B, namely, decreasing spread of the electron wave functions and increasing effective steepness of the confining potential, which reduces the average separation between electrons. Fiz. Tverd. Tela (St. Petersburg) 40, 1753–1759 (September 1998)     

Ionization self-channeling of modulated plasma-wave beams in a magnetic field

The dynamics of ionization self-channeling of modulated beams of plasma waves forming a solitary plasma-wave channel in an external magnetic field is investigated. It is shown that electromagnetic wave processes at the modulation frequencies of the ionizing radiation can be excited in the background plasma and in the channel. Zh. éksp. Teor. Fiz. 113, 1289–1298 (April 1998)     

Motion of a particle in a static magnetic field and in the field of a electromagnetic plane wave

The solutions of the equations of motion of a charged particle in an external electromagnetic field consisting of a superposition of a constant uniform magnetic field and the field of a circularly polarized electromagnetic plane wave are presented as solutions of the Cauchy problem. The resonance case is studied. Zh. Tekh. Fiz. 67, 94–99 (February 1997)     

Motion of a particle in a static magnetic field and the field of a monochromatic electromagnetic plane wave

A solution of the equation of motion of a charged particle in an external electromagnetic field comprising a superposition of a uniform static magnetic field and the field of a monochromatic, elliptically polarized electromagnetic plane wave is obtained as the solution of a Cauchy problem. The resonance case is investigated. An analysis of the resulting solution is given. Zh. Tekh. Fiz. 69, 106–110 (May 1999)     

Propagation of waves in nonlocal porous multi-phase nanocrystalline nanobeams under longitudinal magnetic field

ABSTRACT

This article investigates wave propagation behavior of a multi-phase nanocrystalline nanobeam subjected to a longitudinal magnetic field in the framework of nonlocal couple stress and surface elasticity theories. In this model, the essential measures to describe the real material structure of nanocrystalline nanobeams and the size effects were incorporated. This non-classical nanobeam model contains couple stress effect to capture grains micro-rotations. Moreover, the nonlocal elasticity theory is employed to study the nonlocal and long-range interactions between the particles. The present model can degenerate into the classical model if the nonlocal parameter, couple stress and surface effects are omitted. Hamilton’s principle is employed to derive the governing equations which are solved by applying an analytical method. The frequencies are compared with those of nonlocal and couple stress-based beams. It is showed that wave frequencies and phase velocities of a nanocrystalline nanobeam depend on the grain size, grain rotations, porosities, interface, magnetic field, surface effect and nonlocality.     

New types of collective spin-wave excitations in magnetic metallic superlattices

The necessary conditions under which the phonon and electron mechanisms of interlayer exchange combine to form new types of both surface and volume collective spin-wave excitations in a magnetic superstructure of the magnet-nonmagnetic-metal type are given. As an example, a new type of doubly-partial generalized surface spin wave and a new type of inhomogeneous spin-spin resonance are found for superlattices of the antiferromagnet-nonmagnetic-metal type. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 4, 232–236 (25 February 1996)     

Andreev levels of SNS-junctions in weak magnetic fields

Spatial quantization of the energy spectrum of quasiparticles, bound by Andreev scattering in the normal layer of SNS junctions, remains observable in weak constant magnetic fieldsH parallel to the phase boundaries. Quasiparticles, especially in the low lying Andreev states, can traverse thick normal regions many thousand times before they are scattered once by interaction withH . This confirms the expectation that quasiparticle transport phenomena in superconducting heterostructures should be little influenced by magnetic fields as long as the cyclotron radius greatly exceeds the average spatial extension of the unperturbed wave functions normal to the phase boundaries.     

Dirac particle with anomalous magnetic moment in a plane-polarized wave and stationary transverse magnetic and electric fields

A determination is made of the wave function of an uncharged Dirac particle with an anomalous magnetic moment in a plane-polarized wave and stationary magnetic and electric fields. The stationary magnetic field is parallel to the magnetic field of the wave and perpendicular to the stationary electric field. Institute of Chemical Physics and Combustion. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 66–69, May, 1998.     

High-frequency phenomena in organic conductors in a magnetic field

The propagation of electromagnetic waves in organic layered conductors with metallic conductance and a quasi-two-dimensional electron energy spectrum of arbitrary form is studied theoretically. The depth of penetration of the electromagnetic field into the conductor is found, and it is discovered to be sensitive to the polarization of the incident wave. This is done for an arbitrarily oriented (with respect to the layers) magnetic field so strong that the radius of curvature of the electron path is much smaller than the electron’s mean free path. It is established that studying these effects in experiments can reveal in detail the shape and dimensions of the Fermi surface and the relaxation properties of the conduction electrons. Zh. éksp. Teor. Fiz. 114, 676–686 (August 1998)     

Ground states of the hydrogen molecule and its molecular ion in the presence of a magnetic field using the variational Monte Carlo method

ABSTRACT

By using the variational Monte Carlo (VMC) method, we calculated the 1sσ_g-state energies, the dissociation energies, and the binding energies of the hydrogen molecule and its molecular ion in the presence of an aligned magnetic field regime between 0 and 10?a.u. The present calculations are based on using two types of compact and accurate trial wave functions, which are put forward for consideration in calculating energies in the absence of a magnetic field. The obtained results are compared with the most recent accurate values. We conclude that the applications of the VMC method can be successfully extended to cover the case of molecules under the effect of a magnetic field.     

Macro-scale matter wave generation in charged particle dynamics in a magnetic field,a consequence of quantum entanglement

Matter wave interference effects on the macro-scale predicted by the author in charged particle dynamics in a magnetic field [R.K. Varma, Phys. Rev. E 64, 036608 (2001)], and observed subsequently [R.K. Varma, A.M. Punithavelu, S.B. Banerjee, Phys. Rev. E 65, 026503 (2002); R.K. Varma, S.B. Banerjee, Phys. Scr. 75, 19 (2007)] have been shown here to be an interesting consequence of quantum entanglement between the parallel and perpendicular degrees of freedom of the particle. Treating the problem in the framework of the inelastic scattering theory, it is shown that these macro-scale matter waves are generated in the ‘parallel’ degree of freedom as a modulation of the plane wave state of the particle along the field concomitantly with the excitation of Landau levels in the perpendicular degree of freedom in an inelastic scattering episode. We highlight here the role of quantum entanglement leading to the generation of this macro-scale quantum entity which has been shown to exhibit observable consequences. This case also exemplifies a situation exhibiting quantum entanglement on the macro-scale.     

Pulsed magnetic resonance as a probe of longitudinal spin waves and magnetic second sound

Under appropriate conditions, longitudinal spin waves and spin wave second sound, a magnetic temperature wave, can be observed in quantum liquids and solid using pulsed magnetic resonance. A “hole-burning” experiment yields directly the spectrum ω(k) of the propagating magnetic wave.