Influence Of Local Magnetic Field Research Articles

Kinetic study of transverse electron-scale interface instability in relativistic shear flows

Interfacial magnetic field structures induced by transverse electron-scale shear instability (mushroom instability) are found to be strongly associated with electron and ion dynamics, which in turn will influence the development of the instability itself. We find that high-frequency electron oscillations are excited normal to the shear interface. Also, on a larger time scale, the bulk of the ions are gradually separated under the influence of local magnetic fields, eventually reaching an equilibrium related to the initial shear conditions. We present a theoretical model of this behavior. Such separation on the scale of the electron skin depth will prevent different ions from mixing and will thereafter restrain the growth of higher-order instabilities. We also analyze the role of electron thermal motion in the generation of the magnetic field, and we find an increase in the instability growth rate with increasing plasma temperature. These results have potential for providing a more realistic description of relativistic plasma flows.

Thermal radiation therapy of biomagnetic fluid flow in the presence of localized magnetic field

Present work describes the applications of magnetic field and thermal radiation on the two-dimensional, unsteady flow of bio-magnetic fluid (blood) in a rectangular vessel. The viscosity of the fluid is considered to be an exponential function of temperature. The radiative heat flux is approximated with the help of Stefan Boltzmann law, which is a nonlinear function of temperature. The governing nonlinear, coupled system of partial differential equations for the underlying problem is represented in terms of stream function-vorticity formulation, which is further solved numerically with the help of upwind scheme along with successive over relaxation method. For the validation of the solutions, results are compared with the numerical and experiemental data available in the literature. In order to notice the influence of localized magnetic field and thermal radiation, solutions are presented graphically in terms of streamlines, isotherms, vorticity function contours and velocity component contours and are discussed both qualitatively and quantitatively from the physiological point of view.

Electronic functionality of Gd-bisphthalocyanine: Charge carrier concentration, charge mobility, and influence of local magnetic field

Gadolinium bisphthalocyanine (GdPc2) has been placed among the highest ranked molecular materials considered namely for modern optoelectronic applications including organic solar cells. To improve understanding of the correlation between GdPc2 magnetic properties and its electronic functionality, we experimentally and theoretically studied charge carrier concentration, charge mobility, and influence of local magnetic field on charge carrier transport. For better clearance, all the main studied properties of GdPc2 bisphthalocyanine were compared with Zn phthalocyanine (ZnPc) as a reference material. Conductivity and charge carrier mobility were measured in materials incorporated in FET active channels. UV Vis spectroscopy, Electron Paramagnetic Resonance Spectroscopy, and IR spectroscopy were also applied. The narrow band gap together with small ionization potential of GdPc2 lead to high free charge carrier concentration. Among parameters affecting charge carrier mobility, molecular arrangement and intermolecular and intramolecular charge carrier pathways were highlighted. The possibility that the interaction of the mobile charge carriers with the local magnetic field of GdPc2 molecules reduces charge carrier mobility is also discussed.

Influence of localized magnetic field and strong viscosity on the biomagnetic fluid flow in a rectangular channel

In this paper biomagnetic fluid flow in a rectangular enclosure is studied under the influence of applied magnetic field and temperature-dependent viscosity. An electrically conducting magnetic fluid (blood) is considered here which also exhibits magnetization. It is assumed that the magnetization M¯ of the fluid is varying linearly with temperature T¯ and magnetic field intensity H¯. The viscosity μ¯ of biofluid is taken to be an exponential function of temperature. The mathematical model for the present problem results in a nonlinear and coupled system of equations and is given in stream function-vorticity-temperature formulation for the purpose of numerical treatment. Solutions are obtained iteratively by employing upwind scheme together with successive over relaxation method. Numerical results are presented in terms of average Nusselt number, streamlines, isotherms and vorticity function contours indicating that presence of magnetic source and viscosity variations influences the flow field considerably. It is found that the strength of the vortices and the temperature increases by magnifying the magnetic intensity and circular contours are generated extensively for the blood having variable viscosity.

Magnetic scanning gate microscopy of CoFeB lateral spin valve

Devices comprised of CoFeB nanostructures with perpendicular magnetic anisotropy and non-magnetic Ta channel were operated in thermal lateral spin valve (LSV) mode and studied by magnetotransport measurements and magnetic scanning gate microscopy (SGM). Due to the short spin diffusion length of Ta, the spin diffusion signal was suppressed, allowing the study of the contribution from the anomalous Nernst (ANE) and anomalous Hall effects (AHE). The magnetotransport measurements identified the switching fields of the CoFeB nanostructures and demonstrated a combination of AHE and ANE when the devices were operated in thermally-driven spin-injection mode. Modified scanning probe microscopy probes were fabricated by placing a NdFeB magnetic bead (MB) on the apex of a commercial Si probe. The dipole magnetic field distribution around the MB was characterized by using differential phase contrast technique and direct measurement of the switching field induced by the bead in the CoFeB nanodevices. Using SGM we demonstrate the influence of localized magnetic field on the CoFeB nanostructures near the non-magnetic channel. This approach provides a promising route towards the study of thermal and spin diffusion effects using local magnetic fields.

The CoRoT chemical peculiar target star HD 49310

Context. The magnetic chemically peculiar (CP) stars of the upper main sequence are well-suited laboratories for investigating the influence of local magnetic fields on the stellar surface because they produce inhomogeneities (spots) that can be investigated in detail as the star rotates. Aims. We studied the inhomogeneous surface structure of the CP2 star HD 49310 based on high-quality CoRoT photometry obtained during 25 days. The data have nearly no gaps. This analysis is similar to a spectroscopic Doppler-imaging analysis, but it is not a tomographic method. Methods. We performed detailed light-curve fitting in terms of stationary circular bright spots. Furthermore, we derived astrophysical parameters with which we located HD 49310 within the Hertzsprung-Russell diagram. We also investigated the possible connection of this star to the nearby young open cluster NGC 2264. Results. With a Bayesian technique, we produced a surface map that shows six bright spots. After removing some artefacts, the residuals of the observed and synthetic photometric data are ±0.123 mmag. The rotational period of the star is P = 1.91909 ± 0.00001 days. Our photometric observations therefore cover about 13 full rotational cycles. Three spots are very large with diameters of � 40 deg. The spots are brighter by 40% than the unperturbed stellar photosphere. Conclusions. HD 49310 is a classical silicon (CP2) star with a mass of about 3 M� . It is not a member of NGC 2264. Our analysis shows the potential of using high-quality photometric data to analyse the surface structure of CP stars. A comprehensive analysis of similar archival data, preferrably from space missions, would contribute significantly to our understanding of surface phenomena of CP stars and their temporal evolution.

Spin-dependent transport between magnetic nanopillars through a nano-granular metal matrix

We investigate the influence of local magnetic field on the spin-dependent transport properties of magnetic granular metals. By means of electron-beam-induced-deposition we fabricate a complex granular system made of Co nanopillars embedded in a Pt-C nano-granular metal matrix. We identify two different spin-dependent tunnelling regimes. In the first one, transport occurs almost exclusively through the nano-granular Pt-C matrix and it is affected by the local stray field due to the Co nanopillars. In the second regime, the transport takes place through both the Pt-C matrix and the Co nanopillars. These two transport regimes are discriminated by the different sign of the magnetoresistance. In particular, a strong enhancement of the magnetoresistance is found at low temperatures in the second regime, which is caused by spin-flip scattering and higher order tunnelling processes.

Influence of Local Magnetic Fields on P-Doped Si Floating Zone Melting Crystal Growth in Microgravity

A two-dimensional axisymmetric numerical model is presented to study the influence of local magnetic fields on P-doped Si floating zone melting crystal growth in microgravity. The model is developed based on the finite difference method in a boundary-fitted curvilinear coordinate system. Extensive numerical simulations are carried out, and parameters studied include the curved growth interface shape and the magnetic field configurations. Computed results show that the local magnetic field is more effective in reducing the impurity concentration nonuniformity at the growth interface in comparison with the longitudinal magnetic field. Moreover, the curved growth interface causes more serious impurity concentration nonuniformity at the growth interface than the case with a planar growth interface.