Observation of the spin-Seebeck effect in a ferromagnetic semiconductor
Observation of the spin-Seebeck effect in a ferromagnetic semiconductor
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DOI：
10.1038/nmat2860
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发表时间：
2010-11-01
期刊：
影响因子：
41.2
通讯作者：
Myers, R. C.
中科院分区：
文献类型：
--
作者：
Jaworski, C. M.;Yang, J.;Myers, R. C.
减少传统电子器件中产生的热量是发展基于自旋的电子学（称为自旋电子学）的主要动机。不严格依赖静电势垒升高或降低的基于自旋的晶体管能够克服基于电荷的晶体管的缩放极限。半导体中的自旋输运可能还会通过纯自旋流实现无耗散的信息传递。尽管有这些热力学优势，但关于固体中自旋输运的热学方面的实验文献却很少。一个近期令人惊讶的例外是自旋塞贝克效应的发现，据报道这是对由温度梯度引起的坡莫合金（NiFe）样品长度方向上自旋重新分布的一种测量。令人惊讶的是，这种自旋的宏观空间分布比自旋扩散长度大很多个数量级，这引发了人们对自旋输运热学方面的浓厚兴趣。在此，在铁磁半导体GaMnAs中观察到了自旋塞贝克效应，这使得磁化方向能够灵活设计、自旋极化更大，并且能够在磁相变过程中进行测量。即使在没有纵向电荷输运的情况下也能观察到这种效应。自旋流的空间分布在电断路处仍能保持，突出了这种热驱动效应的局域性。
Reducing the heat generated in traditional electronics is a chief motivation for the development of spin-based electronics, called spintronics(1). Spin-based transistors that do not strictly rely on the raising or lowering of electrostatic barriers can overcome scaling limits in charge-based transistors(2). Spin transport in semiconductors might also lead to dissipation-less information transfer with pure spin currents(3). Despite these thermodynamic advantages, little experimental literature exists on the thermal aspects of spin transport in solids. A recent and surprising exception was the discovery of the spin-Seebeck effect, reported as a measurement of a redistribution of spins along the length of a sample of permalloy (NiFe) induced by a temperature gradient(4). This macroscopic spatial distribution of spins is, surprisingly, many orders of magnitude larger than the spin diffusion length, which has generated strong interest in the thermal aspects of spin transport(5). Here, the spin-Seebeck effect is observed in a ferromagnetic semiconductor, GaMnAs, which allows flexible design of the magnetization directions, a larger spin polarization, and measurements across the magnetic phase transition. This effect is observed even in the absence of longitudinal charge transport. The spatial distribution of spin currents is maintained across electrical breaks, highlighting the local nature of this thermally driven effect.