Catalan Institute of Nanotechnology (ICN-CIN2), E-08193 Barcelona, Spain.
Nature. 2011 Aug 11;476(7359):189-93. doi: 10.1038/nature10309.
Modern computing technology is based on writing, storing and retrieving information encoded as magnetic bits. Although the giant magnetoresistance effect has improved the electrical read out of memory elements, magnetic writing remains the object of major research efforts. Despite several reports of methods to reverse the polarity of nanosized magnets by means of local electric fields and currents, the simple reversal of a high-coercivity, single-layer ferromagnet remains a challenge. Materials with large coercivity and perpendicular magnetic anisotropy represent the mainstay of data storage media, owing to their ability to retain a stable magnetization state over long periods of time and their amenability to miniaturization. However, the same anisotropy properties that make a material attractive for storage also make it hard to write to. Here we demonstrate switching of a perpendicularly magnetized cobalt dot driven by in-plane current injection at room temperature. Our device is composed of a thin cobalt layer with strong perpendicular anisotropy and Rashba interaction induced by asymmetric platinum and AlOx interface layers. The effective switching field is orthogonal to the direction of the magnetization and to the Rashba field. The symmetry of the switching field is consistent with the spin accumulation induced by the Rashba interaction and the spin-dependent mobility observed in non-magnetic semiconductors, as well as with the torque induced by the spin Hall effect in the platinum layer. Our measurements indicate that the switching efficiency increases with the magnetic anisotropy of the cobalt layer and the oxidation of the aluminium layer, which is uppermost, suggesting that the Rashba interaction has a key role in the reversal mechanism. To prove the potential of in-plane current switching for spintronic applications, we construct a reprogrammable magnetic switch that can be integrated into non-volatile memory and logic architectures. This device is simple, scalable and compatible with present-day magnetic recording technology.
现代计算技术基于将信息编写、存储和检索为磁位。尽管巨磁电阻效应已经改进了存储元件的电读取，但磁写入仍然是主要研究工作的对象。尽管有几项关于通过局部电场和电流反转纳米磁铁极性的方法的报道，但简单地反转高矫顽力的单层铁磁体仍然是一个挑战。具有大矫顽力和垂直磁各向异性的材料是数据存储介质的主要支柱，因为它们能够在长时间内保持稳定的磁化状态并且易于小型化。然而，使材料适合存储的相同各向异性特性也使其难以写入。在这里，我们展示了在室温下通过平面内电流注入驱动的垂直磁化钴点的切换。我们的器件由具有强垂直各向异性和由不对称的铂和 AlOx 界面层引起的 Rashba 相互作用的薄钴层组成。有效切换场垂直于磁化方向和 Rashba 场。切换场的对称性与 Rashba 相互作用引起的自旋积累以及在非磁性半导体中观察到的自旋相关迁移率以及铂层中的自旋霍尔效应引起的扭矩一致。我们的测量表明，切换效率随钴层的磁各向异性和铝层的氧化增加而增加，这表明 Rashba 相互作用在反转机制中起着关键作用。为了证明平面内电流切换在自旋电子学应用中的潜力，我们构建了一个可重新编程的磁开关，该开关可以集成到非易失性存储器和逻辑架构中。该器件简单、可扩展且与当前的磁记录技术兼容。
