Resonance magnetoplasticity in the EPR scheme under ultralow magnetic fields

Resonance relaxation displacements of dislocations in NaCl crystals exposed to crossed ultralow magnetic fields (static field B = 26–261 μT and radiofrequency field B ～ 3 μT) in the electron paramagnetic resonance scheme are studied. The effect is also observed in the magnetic field of the Earth when crossed with a pulsed pump field with a resonance duration of ～0.5 μs. Changes in the microhardness of crystals of ZnO, triglycine sulfate, and potassium hydrogen phthalate after their exposure to the magnetic field of the Earth and the orthogonally directed pump field are found out.     

A study of the microwave dielectric permittivity of liquid crystals in electric and magnetic fields

A microwave detector based on a self-sustained oscillator circuit is proposed as a means to investigate the real and imaginary components of the dielectric permittivity of liquid crystals in external electric and magnetic fields. Results are given for measurements of a 500 MHz oscillator frequency for two types of nematic crystals, 5CBP and MBBA. Fundamental regularities are identified in the behavior of the microwave dielectric permittivity of samples in electric and magnetic fields. It is shown that the minimum of the high-frequency dielectric loss in liquid crystals correspond to a situation in which the long axes of the molecules are oriented parallel to the direction of the microwave electric field. Zh. Tekh. Fiz. 68, 117–121 (January 1998)     

Effect of a magnetic field on the microhardness of ferromagnetic fields

The microhardness of ferromagnets is studied as a function of an external magnetic field. The maximum values of the relative change in microhardness during measurement without a field and in a magnetic saturation field for low-carbon iron, Kh16 steel, and the powder alloys Fe-TiC (ferroTiC) and PG-KhN80SR-4 are 20–34%. The effect of various processes of change in the magnetic structure on the measured microhardness of the ferromagnet is examined. A relation is established between the effect and the change in magnetic energy due to external stresses.Tula State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 30–33, September, 1994.     

Surface polaritons in a dielectric at a boundary with a metal in crossed electric and magnetic fields

AbstractThe spectrum of surface polaritons in a dielectric at a boundary with an ideal metal or a super-conductor in crossed constant electric and magnetic fields is studied. It is shown that the polariton spectrum possesses strong nonreciprocity (polaritons with fixed frequency propagate only in one direction; this is the rectification effect) and depends strongly on the directions of the external fields and their ratios H ₀/E ₀.     

Effect of a pulsed magnetic field on the microhardness of C60 single crystals

Magnetic-field pulses with induction greater than 10 T were observed to influence the microhardness of C₆₀ single crystals. It was established that the magnetic field reversibly alters the bulk properties of the material. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 2, 110–113 (25 January 1999)     

Effect of magnetic field in the microhardness studies on calcium hydrogen phosphate crystals

Calcium hydrogen phosphate dihydrate (CaHPO₄·2H₂O, brushite) crystals are grown in gel medium at physiological pH by single diffusion method in the presence of different magnetic field strengths, namely 0, 0.1 and 0.2 Tesla. The results indicate that in the presence of magnetic field, the number of brushite crystals formed at the gel-solution interface reduces and the average size of the crystals increases. This shows that the growth of brushite crystal was favored by magnetism. Vickers and Knoop microhardness studies were carried out on the crystals grown at various magnetic fields. The Vickers (H_V) and Knoop (H_K) microhardness numbers were found to increase with increasing load. The values of Meyer’s index number (n) decrease while the magnetic field strength increases. Nevertheless the n values are greater than 1.6, which shows that the brushite crystals grown under magnetic fields still fall in the soft material category. The brittle index (Bi), yield strength (σ_y) and elastic stiffness constant (c₁₁) were calculated. The Young’s Modulus was calculated using the Knoop hardness value and found to decrease in higher magnetic field strengths.     

Optics of magnetoelectric media in the presence of a magnetic field and a spatial dispersion of the dielectric permittivity

Influence of an external magnetic field and a spatial dispersion of the dielectric permittivity on the irreversibility of waves in magnetoelectric media is considered. Features of the azimuth inhomogeneity at the simultaneous anisotropy of the dielectric permittivity and magnetic permeability in these media are studied.     

Effect of electric field on the dielectric permittivity of betaine phosphite crystals in the paraelectric phase

Temperature dependences of the dielectric permittivity of betaine phosphite crystals are studied both without and under application of an electric bias. It is shown that, in view of the fact that the high-temperature improper ferroelastic (antiferrodistorsive) phase transition at T _c1=355 K is nearly tricritical, the nonlinear temperature dependence of inverse dielectric permittivity in the paraelectric phase and the effect of the field on the dielectric permittivity can be described within a phenomenological model containing two coupled (polar and nonpolar) order parameters with a negative coupling coefficient. An analysis of the model revealed that, in the case where two phase transitions, a nonpolar and a ferroelectric one, can occur in the crystal, all of its dielectric properties, including the polarization response in a field, can be described by one dimensionless parameter a. For the crystal under study, we have a=?2.5. This value of the parameter corresponds to a second-order ferroelectric transition far from the tricritical point, at which a=?1. It is shown that the polarization response in the paraelectric phase in an electric field calculated within this model differs radically from that in the ferroelectric phase-transition model for which the Curie-Weiss law holds in the paraelectric phase.     

Quartet of resonance peaks of dislocation displacements in NaCl crystals during their magnetic processing in the low-frequency EPR scheme

Resonance relaxation displacements of dislocations have been studied in NaCl crystals placed in crossed ultralow magnetic fields have been studied in the electron paramagnetic resonance (EPR) scheme, i.e., in the static magnetic field B = (26–261) μT and the perpendicular radio-frequency field (with the amplitudes of 2.5 and 6 μT in the frequency range ν = (0.5–7.3) MHz). The spectrum (quartet) of equidistant resonance peaks of the dislocation mean paths l(ν) has been observed. In the most part of the studied field interval B, the frequencies of the EPR peaks correspond to the Zeeman splitting of the levels with four g-factors close to 2 and the difference of the neighboring values Δg = 0.09. The equidistance is violated only at the lowest fields, B < 50 μT, and frequencies ν < 0.7 MHz.     

An EPR study of the orientational transition in smectic liquid crystals in a magnetic field

Spin probe EPR spectroscopy is used to detect an orientational transition in the smectic mesophase in 4-n-octyl-4'-cyanobiphenyl (8CB) liquid crystal under the action of an intense magnetic field (5.87 T).     

Polariton dynamics of a one-dimensional magnetic photonic crystal in crossed magnetic and electric fields

By an example of a semibounded one-dimensional magnetic photonic crystal (MPC) of easy-axis antiferromagnet-nonmagnetic dielectric type placed in mutually orthogonal dc magnetic and electric fields, conditions are found under which the quadratic magneto-optic interaction leads to a number of anomalies in the reflection and propagation conditions for TM or TE waves incident from outside on the surface of the superlattice. It is assumed that the easy magnetic axis is collinear to the electric field.     

Short-term exposure to a 1.5 tesla static magnetic field does not affect somato-sensory-evoked potentials in man

The literature is contradictory regarding the effect of static magnetic fields on the function of the central nervous system of mammals. Since human subjects are exposed to intense static magnetic fields during magnetic resonance imaging, it is important to determine if the static magnetic field adversely affects the nervous system of man. Therefore, somato-sensory evoked potentials (SEPs) elicited from median nerve stimulation were measured in 11 normal subjects before and during short-term exposure to a 1.5 Tesla static magnetic field. Specially modified instrumentation was used to record SEPs that were unperturbed by the static magnetic field. There were no statistically significant differences in the N20 or P25 latencies or in the amplitude from N20 negative peak to P25 positive peak of the SEPs obtained before compared to those recorded during exposure to the static magnetic field. In addition, there were no changes in the waveforms associated with exposure to the static magnetic field. We conclude that short-term exposure to a 1.5 Tesla static magnetic field does not affect SEPs (i.e., nerve conduction and synaptic transmission were within normal limits) in normal human subjects.     

The theory of a rotating plasma in crossed electric and magnetic fields

The paper presents an analysis of the behaviour of a weakly ionized gas confined by cylindrical electrodes and dielectric fronts. An ionized gas is put into a rotational movement by transverse electric and longitudinal magnetic fields. Quantities describing a plasma in the stationary state have been obtained by solving a system of macroscopic equations. Some of them are compared with experimental data.I would like to express my thanks to ing. L. ípek CSc for providing me with the experimental data obtained with the device BXE1. My thanks are also due to ing. V. Kopecký CSc for valuable comments.     

Electronic properties of a Weyl semimetal in crossed magnetic and electric fields

The study of Weyl semimetals is one of the most challenging problems of condensed matter physics. These materials exhibit interesting properties in a magnetic field. In this work, we investigate the Landau bands and the density of states (DOS) oscillations in a Weyl semimetal in crossed magnetic and electric fields. An expression is obtained for the energy spectrum of the system using the following three different methods: an algebraic approach, a Lorentz shift-based approach, and a quasi-classical approach. It is interesting that the energy spectrum calculated in terms of the quasi-classical approach coincides with the spectrum obtained using the microscopic approaches. An electric field is shown to change the Landau bands radically. In addition, the classical motion of a three-dimensional Dirac fermion in crossed fields is studied. In the case of a Dirac spectrum, the longitudinal (with respect to magnetic field) component of momentum (p _z ∥ H) is shown to be an oscillating function of the magnetic field. When the electric field is v⊥H/c, the Landau levels collapse and the motion becomes fully linear in an unusual manner. In this case, the wavefunction of bulk states vanishes and only states with p _z = 0 are retained. An electric field affects the character of DOS oscillations. An analytical expression is obtained for the quantum capacitance in crossed fields in the cases of strong and weak electric fields. Thus, an electric field is an additional parameter for adjusting the diamagnetic properties of Weyl semimetals.     

Fetal development of mice following intrauterine exposure to a static magnetic field of 6.3 T.

The study was undertaken to investigate possible teratogenic effects of a high magnetic field on fetal development in mice. Eighty-four pregnant CD-1 mice (ICR) were exposed to a static magnetic field of 6.3 T for 1 hr a day from day 7 through day 14 of gestation, a period corresponding to major organogenesis. Fifty mice served as controls. Dams were sacrificed on day 18 of gestation. Fetuses were examined for both external and skeletal abnormalities. No significant differences between exposed and control groups were observed regarding litter size, fetal weight, intrauterine mortality rate, or external and skeletal anomalies. The effects of static magnetic field of 6.3 T on the parameters studied appear negligible.     

Orbital magnetic moment of a quantum well and a quantum dot in crossed magnetic and electric fields

A new physical effect, namely, oscillations of the orbital magnetic moment with a change in the electric field strength in two types of nanostructures, has been predicted. Explicit analytical expressions for the orbital magnetic moment of a quantum well and a quantum dot in crossed magnetic and electric fields have been derived. The oscillations of the orbital magnetic moment with a change in the electric and magnetic fields have been studied. The oscillation periods in both the electric and magnetic fields have been found and the limiting cases of the strong magnetic and quantum confinement effects have been considered.     

带电粒子在相互垂直的匀强电场和磁场中的运动轨迹

推导出带电粒子在相互垂直的匀强电场和磁场中普遍情况下的运动方程,给出了几种典型情况下的轨迹,并对轨迹的形状和性质,结点的出现进行了讨论.     

Wave function of a charged particle in crossed electrostatic and variable magnetic fields

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