CURRENT-DRIVEN MAGNONS IN MAGNETIC MULTILAYERS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 2957-2957
Author(s):  
M. TSOI
Keyword(s):  
Electric Current ◽  
Driving Force ◽  
Current Flow ◽  
Point Contact ◽  
Magnetic Multilayers ◽  
Fluctuation Phenomena ◽  
Adjacent Layer ◽  
Acoustic Wave Generation ◽  
Current Densities ◽  
Spin Momentum

Spin waves, or magnons, are intrinsic excitations in magnetic materials and have attracted considerable attention since introduced by Bloch in 1930.1 Recently ideas of spintronics have impacted this field dramatically. Berger2 and Sloczewski3 introduced completely new aspects of the physics of metallic ferromagnets in the presence of an electric current of high density. Excitation of magnons by an electric current has been predicted and seen in magnetic multilayers,4-6 where the driving force for the excitations is the spin-momentum transfer associated with an electric current flow. We have developed a microcontact technique (magnetic microcontact spectroscopy) to investigate the current-driven magnon generation.4,5 In our experiments we inject current densities as high as 109 A/cm2 into a Co/Cu multi-layer through a point contact made using a sharpened Ag wire carefully brought into contact with a multi-layer file. We observe current-driven magnons in multi-layers with both ferromagnetic4,5 and antiferromagnetic7 configuration of the adjacent layer magnetizations. Some further interesting applications of the technique, particularly, for studying fluctuation phenomena, resonant magnon generation, acoustic wave generation, etc., will be presented.

scholarly journals Thermal and non-thermal effects of capacitive–resistive electric transfer application on different structures of the knee: a cadaveric study

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jacobo Rodríguez-Sanz ◽  
Albert Pérez-Bellmunt ◽  
Carlos López-de-Celis ◽  
Orosia María Lucha-López ◽  
Vanessa González-Rueda ◽  
...  
Keyword(s):  
Low Power ◽  
Electric Current ◽  
Thermal Effects ◽  
Sports Medicine ◽  
Current Flow ◽  
In Vitro Study ◽  
Science Data ◽  
Fresh Frozen ◽  
Inflammatory Processes

AbstractCapacitive–resistive electric transfer therapy is used in physical rehabilitation and sports medicine to treat muscle, bone, ligament and tendon injuries. The purpose is to analyze the temperature change and transmission of electric current in superficial and deep knee tissues when applying different protocols of capacitive–resistive electric transfer therapy. Five fresh frozen cadavers (10 legs) were included in this study. Four interventions (high/low power) were performed for 5 min by a physiotherapist with experience. Dynamic movements were performed to the posterior region of the knee. Capsular, intra-articular and superficial temperature were recorded at 1-min intervals and 5 min after the treatment, using thermocouples placed with ultrasound guidance. The low-power protocols had only slight capsular and intra-capsular thermal effects, but electric current flow was observed. The high-power protocols achieved a greater increase in capsular and intra-articular temperature and a greater current flow than the low-power protocols. The information obtained in this in vitro study could serve as basic science data to hypothesize capsular and intra-articular knee recovery in living subjects. The current flow without increasing the temperature in inflammatory processes and increasing the temperature of the tissues in chronic processes with capacitive–resistive electric transfer therapy could be useful for real patients.

Shear-layers in magnetohydrodynamic spherical Couette flow with conducting walls

2010 ◽  
Vol 645 ◽  
pp. 145-185 ◽  
Author(s):  
A. M. SOWARD ◽  
E. DORMY
Keyword(s):  
Magnetic Field ◽  
Shear Layer ◽  
Electric Current ◽  
Current Flow ◽  
Outer Boundary ◽  
Free Shear Layer ◽  
Viscous Effects ◽  
Current Leakage ◽  
Axisymmetric Motion ◽  
Relative Conductance

We consider the steady axisymmetric motion of an electrically conducting fluid contained within a spherical shell and permeated by a centred axial dipole magnetic field, which is strong as measured by the Hartmann number M. Slow axisymmetric motion is driven by rotating the inner boundary relative to the stationary outer boundary. For M ≫ 1, viscous effects are only important in Hartmann boundary layers adjacent to the inner and outer boundaries and a free shear-layer on the magnetic field line that is tangent to the outer boundary on the equatorial plane of symmetry. We measure the ability to leak electric current into the solid boundaries by the size of their relative conductance ɛ. Since the Hartmann layers are sustained by the electric current flow along them, the current inflow from the fluid mainstream needed to feed them increases in concert with the relative conductance, because of the increasing fraction ℒ of the current inflow leaked directly into the solids. Therefore the nature of the flow is sensitive to the relative sizes of ɛ−1 and M.The current work extends an earlier study of the case of a conducting inner boundary and an insulating outer boundary with conductance ɛo = 0 (Dormy, Jault & Soward, J. Fluid Mech., vol. 452, 2002, pp. 263–291) to other values of the outer boundary conductance. Firstly, analytic results are presented for the case of perfectly conducting inner and outer boundaries, which predict super-rotation rates Ωmax of order M1/2 in the free shear-layer. Successful comparisons are made with numerical results for both perfectly and finitely conducting boundaries. Secondly, in the case of a finitely conducting outer boundary our analytic results show that Ωmax is O(M1/2) for ɛo−1 ≪ 1 ≪ M3/4, O(ɛo2/3M1/2) for 1 ≪ ɛo−1 ≪ M3/4 and O(1) for 1 ≪ M3/4 ≪ ɛo−1. On increasing ɛo−1 from zero, substantial electric current leakage into the outer boundary, ℒo ≈ 1, occurs for ɛo−1 ≪ M3/4 with the shear-layer possessing the character appropriate to a perfectly conducting outer boundary. When ɛo−1 = O(M3/4) the current leakage is blocked near the equator, and the nature of the shear-layer changes. So, when M3/4 ≪ ɛo−1, the shear-layer has the character appropriate to an insulating outer boundary. More precisely, over the range M3/4 ≪ ɛo−1 ≪ M the blockage spreads outwards, reaching the pole when ɛo−1 = O(M). For M ≪ ɛo−1 current flow into the outer boundary is completely blocked, ℒo ≪ 1.

Electrode conduction processes in air plasmas

1962 ◽  
Vol 13 (3) ◽  
pp. 465-477 ◽  
Author(s):  
D. W. George ◽  
H. K. Messerle
Keyword(s):  
Magnetic Field ◽  
Shock Tube ◽  
Current Flow ◽  
Electronic Conductivity ◽  
The Other ◽  
High Current ◽  
Air Plasma ◽  
Air Plasmas ◽  
Current Densities

Using an electrically driven shock tube with initial pressures of 0.1 to 1.0 mm Hg and shock speeds of about Mach 12 to 15, the resistance of an air plasma between two parallel probes has been measured by two different techniques and the results compared. In one, external voltages of from 0 to 100 V were applied to the probes and in the other, electromagnetically induced voltages of from 0 to 25 V were produced by the plasma's motion in a magnetic field of up to 3500 G. In either case the resistance was found to decrease as the current flow increased and was consistent with the equilibrium electronic conductivity of the air plasma at high current densities.

Simulation of the Electric Current Flow in Amorphous-Crystalline Ti2NiCu Alloy with Shape Memory Effect

2016 ◽  
Vol 845 ◽  
pp. 146-149
Author(s):  
Dmitriy S. Kuchin ◽  
Victor V. Koledov ◽  
Pavel V. Bogun ◽  
Peter V. Lega ◽  
Vedamanickam Sampath ◽  
...  
Keyword(s):  
Electric Current ◽  
Current Flow ◽  
Amorphous Matrix ◽  
Volume Fraction ◽  
Current Density Distribution ◽  
Heat Evolution ◽  
Equatorial Region ◽  
Joule Heat ◽  
Electric Pulses ◽  
Electric Current Flow

A new technique for the production of nanograined alloys from rapidly quenched amorphous ribbons by serial electric pulses has been proposed recently [1]. The present work involves a theoretical study of electric current flow in a nonhomogeneous Ti2NiCu alloy consisting of an amorphous matrix with a crystalline phase of spherical morphology embedded in it. The electric current density distribution was calculated in the vicinity of a spherical nucleus, which has an electrical resistance that is only 0.4 times that of the amorphous matrix. The calculation of Joule heat density was done in the nucleus and in the amorphous volume surrounding it. It was shown that during the current pulse the Joule heat evolution in nucleus exceeds one in equatorial region in matrix, but less than near the poles. The dependence of relative resistivity of nonhomogeneous amorphous-crystalline alloy on volume fraction of spherical crystalline nuclei was calculated

Alternative Control of an Electrically Assisted Tensile Forming Process Using Current Modulation

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Joshua J. Jones ◽  
Laine Mears
Keyword(s):  
Electric Current ◽  
Current Flow ◽  
Current Level ◽  
Temperature Gradients ◽  
Material Strength ◽  
Alternative Control ◽  
Forming Process ◽  
Control Material ◽  
Model Based Control ◽  
Electrically Assisted

Electrically assisted forming is a technique whereby metal is deformed while simultaneously undergoing electric current flow. Using this process, electric current level becomes a new degree of freedom for process control. In this work, we present some alternative control architectures allowing for new avenues of control using such a process. The primary findings are architectures to allow for forming at constant force and forming at constant stress levels by modulating electric current to directly control material strength. These are demonstrated in a tensile forming operation, and found to produce the desired results. Combining these control approaches with previous and contemporary efforts in modeling of the process physics will allow for system identification of material response properties and model-based control of difficult-to-observe process parameters such as real time temperature gradients.

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