A perspective on electrical generation of spin current for magnetic random access memories
A perspective on electrical generation of spin current for magnetic random access memories
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DOI：
10.1063/5.0084551
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发表时间：
2022-01
影响因子：
4
通讯作者：
C. Safranski;Jonathan Z. Sun;A. Kent
中科院分区：
文献类型：
--
作者：
C. Safranski;Jonathan Z. Sun;A. Kent
自旋电流通过改变磁隧道结（MTJ）纳米柱的一个铁磁电极的磁化方向，在磁随机存取存储器（MRAM）器件中写入信息。电荷电流转换成自旋电流的不同物理机制可用于两端和三端器件几何形状。在双端器件中，电荷到自旋转换是通过MTJ铁磁电极中的自旋滤波发生的，目前的MRAM器件工作在理论上预期的最大电荷到自旋转换效率附近。在三端器件中，通道材料中的自旋轨道相互作用也可用于产生大的自旋电流。在这篇展望文章中，我们讨论了能够满足MRAM技术要求的电荷-自旋转换过程。我们强调需要开发具有更大电荷-自旋转换效率的通道材料——可以等于或超过自旋滤波产生的效率——以及具有垂直于通道界面的自旋极化分量的自旋电流。这将使基于直径低于20纳米的垂直磁化MTJ纳米柱的高性能器件无需对称破断场。我们还讨论了CMOS集成所必需的MRAM特性。最后，我们确定了电荷自旋转换测量和度量的关键研究需求，这些测量和度量可用于在完整的MTJ纳米柱器件制造和表征之前优化器件通道材料和界面特性。
Spin currents are used to write information in magnetic random access memory (MRAM) devices by switching the magnetization direction of one of the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) nanopillar. Different physical mechanisms of conversion of charge current to spin current can be used in two-terminal and three-terminal device geometries. In two-terminal devices, charge-to-spin conversion occurs by spin filtering in the MTJ's ferromagnetic electrodes and present day MRAM devices operate near the theoretically expected maximum charge-to-spin conversion efficiency. In three-terminal devices, spin–orbit interactions in a channel material can also be used to generate large spin currents. In this Perspective article, we discuss charge-to-spin conversion processes that can satisfy the requirements of MRAM technology. We emphasize the need to develop channel materials with larger charge-to-spin conversion efficiency—that can equal or exceed that produced by spin filtering—and spin currents with a spin polarization component perpendicular to the channel interface. This would enable high-performance devices based on sub-20 nm diameter perpendicularly magnetized MTJ nanopillars without need of a symmetry breaking field. We also discuss MRAM characteristics essential for CMOS integration. Finally, we identify critical research needs for charge-to-spin conversion measurements and metrics that can be used to optimize device channel materials and interface properties prior to full MTJ nanopillar device fabrication and characterization.