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arXiv 0810.2093cond-mat.mtrl-sci
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双自旋阀的非平衡磁性

Non-equilibrium magnetism in dual spin valves

A. Aziz, O. P. Wessely, M. Ali, D. M. Edwards, C. H. Marrows, B. J. Hickey, M. G. Blamire

摘要:

自旋电子学(spintronics)领域是由发现巨磁电阻(GMR)而引发的,Fert[1]和Grunberg[2]因此获得2007年诺贝尔物理学奖。巨磁电阻是由铁磁物质(FM)对多数和少数自旋电子的差分散射引起的,因此,当被非磁性(NM)间隔物隔开的FM层通过外加场对齐时,电阻与它们反平行时不同。1996年,Slonczewski[3]和Berger[4]预测,大的自旋极化电流可以转移自旋角动量,从而施加足以在稳定磁化状态之间切换薄FM层的自旋转移力矩(STT)[5],并且对于更高的电流密度,驱动发射微波的连续进动[6]。因此,虽然GMR是一种纯粹的被动现象,其最终取决于FM的本征能带结构,但STT向自旋电子学添加了一个有源元件,通过该有源元件可以操纵磁化的方向。在这里,我们表明,高度非平衡自旋注入可以修改的散射不对称性,并通过扩展,FM的内在磁性。这种现象与STT完全不同,它提供了第三种成分,可以进一步扩大自旋电子学应用的机会范围。

英文摘要:

The field of spin electronics (spintronics) was initiated by the discovery of giant magnetoresistance (GMR) for which Fert[1] and Grunberg[2] were awarded the 2007 Nobel Prize for Physics. GMR arises from differential scattering of the majority and minority spin electrons by a ferromagnet (FM) so that the resistance when the FM layers separated by non-magnetic (NM) spacers are aligned by an applied field is different to when they are antiparallel. In 1996 Slonczewski[3] and Berger[4] predicted that a large spin-polarised current could transfer spin-angular momentum and so exert a spin transfer torque (STT) sufficient to switch thin FM layers between stable magnetisation states[5] and, for even higher current densities, drive continuous precession which emits microwaves[6]. Thus, while GMR is a purely passive phenomenon which ultimately depends on the intrinsic band structure of the FM, STT adds an active element to spintronics by which the direction of the magnetisation may be manipulated. Here we show that highly non-equilibrium spin injection can modify the scattering asymmetry and, by extension, the intrinsic magnetism of a FM. This phenomenon is completely different to STT and provides a third ingredient which should further expand the range of opportunities for the application of spintronics.

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