Direct current

Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current. The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage. Direct current may be converted from an alternating current supply by use of a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be converted into alternating current via an inverter. Direct current has many uses, from the charging of batteries to large power supplies for electronic systems, mot

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Alternating current

Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one d

Electric current

An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surf

Voltage

Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds t

Determination of the spin torque non-adiabaticity in perpendicularly magnetized nanowires

Novel nanofabrication methods and the discovery of an efficient manipulation of local magnetization based on spin polarized currents has generated a tremendous interest in the field of spintronics. The search for materials allowing for fast domain wall dynamics requires fundamental research into the effects involved (Oersted fields, adiabatic and non-adiabatic spin torque, Joule heating) and possibilities for a quantitative comparison. Theoretical descriptions reveal a material and geometry dependence of the non-adiabaticity factor beta, which governs the domain wall velocity. Here, we present two independent approaches for determining beta : (i) measuring the dependence of the dwell times for which a domain wall stays in a metastable pinning state on the injected current and (ii) the current-field equivalence approach. The comparison of the deduced beta values highlights the problems of using one-dimensional models to describe two-dimensional dynamics and allows us to ascertain the reliability, robustness and limits of the approaches used.

2012

Extraction of the spin torque non-adiabaticity from thermally activated domain wall hopping

We investigate the non-adiabaticity of current-induced domain wall motion by time resolved analysis of thermally activated domain wall motion between two metastable states within a Co/Pt multilayer wire with a strong uniaxial perpendicular anisotropy. By measuring the dwell times for which the domain wall remains in one state, we deduce the non-adiabaticity factor beta using two independent approaches: (i) the dependence of the dwell times on the injected current and (ii) the current-field equivalency. The comparison of the results allows us to gauge their reliability and the observed differences highlight the importance of the two dimensional (2D) nature of the domain wall. (C) 2011 American Institute of Physics. [doi:10.1063/1.3663215]

2011

Current-induced domain wall motion in Co/Pt nanowires: Separating spin torque and Oersted-field effects

We report on low temperature current induced domain wall depinning experiments on (Co/Pt) multilayer nanowires with perpendicular magnetization. Using a special experimental scheme, we are able to extract the different contributions of the Oersted field and spin torque from the dependence of the depinning field on the injected current for selected magnetization configurations. The spin torque contribution is found to be dominant with a small contribution of the Oersted field leading to a nonadiabaticity factor beta in line with previous measurements. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3405712]

2010