Presence Of Electric Field Gradient Research Articles

Particle motion and drift in non-uniform electric fields

This paper analyzes the two-dimensional motion of a charged particle in constant mutually perpendicular electric and magnetic fields. The magnetic field is assumed to be uniform, and the electric field components are assumed to be linear functions of the Cartesian coordinates. Under these assumptions, the equations of particle motion can be solved analytically. This solution is used to study the stability of particle motion and to assess the accuracy of the guiding center approximation in the presence of electric field gradients. It is well known that if the gradient of a one-dimensional electric field is sufficiently large, the motion of the charged particles becomes unstable and the particles are effectively energized by the electric field. This paper, however, demonstrates that the instability threshold depends on the spatial derivatives of both electric field components and is, under certain conditions, very sensitive to both. The analytical solution is averaged over the gyroperiod to derive simple expressions for the drift speed and the position of the gyrocenter, which explicitly account for the electric field gradient. The results of this averaging are used to develop equations for tracing the particle gyrocenter location, which incorporate the effects of non-uniformity of the electric field. These equations are shown to be noticeably more accurate than those based on the standard E × B drift velocity, which is exact only for uniform electric and magnetic fields. Simple expressions for the local errors in the E × B drift velocity are also derived, which arise from the electric field gradients.

EPR and ENDOR in manganese doped SrTiO3: Electric quadrupole interaction and local disorder

Electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) studies were performed on heavily manganese doped SrTiO3 crystals. At low temperatures (T≈6K), the ENDOR measurements on MnTi4+ show the presence of electric field gradient associated with the electrical polarization. The observation of EPR signals of rhombic Mn2+ complexes remotely compensated in the SrTiO3 lattice is discussed in connection with local disorder in which Mn2+ appears due to the reduction process.

Mössbauer studies of Co xFe 1−xCr 2S 4

The mixed spinel systems Co x Fe 1− x Cr 2S 4 has been studied using the Mössbauer effect. Spectra have been collected over the temperature range 83–300 K. The isomer shifts indicate that the charge states of Fe ions are ferrous in character throughout the series. Absence of quadrupole splitting above the magnetic ordering temperature T c suggests that iron ions occupy only tetrahedral sites. It is notable that as the temperature decreases below T c , both quadrupole shift and asymmetrical line-broadening appear and increase with decreasing temperature, suggesting the presence of electric field gradient and accompanying relaxation effects.