Spin transfer

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In physics, spin transfer is the phenomenon in which the spin angular momentum of the charge carriers (usually electrons) get transferred from one location to another. This phenomenon is responsible for several important and observable physical effects.

Most famously, spin polarized current passing into a nanoscale magnet tends to deposit some of its spin angular momentum into the magnet, thereby applying a large torque to the magnetization. This enables magnetic manipulations far more efficiently than can be achieved with magnetic fields alone, especially as device applications shrink in scale. In the hard disk industry, where a series of nanoscale magnetic layers called a spin valve is often used to measure the small local magnetic fields above the disk surface, this is an obnoxious effect, as it hinders the ability to measure the state of the valve without disturbing it. In the MRAM industry, however, this effect may prove incredibly useful in reducing power consumption. Freescale Semiconductor, Inc. has developed for the first time a field-driven MRAM for commercial consumption, but the world has yet to see a spin-transfer-driven chip.