An ultimate goal of spintronics is to control magnetism via electrical means. One promising way is to utilize a current-induced spin-orbit torque (SOT) originating from the strong spin-orbit coupling in heavy metals and their interfaces to switch a single perpendicularly magnetized ferromagnetic layer at room temperature. However, experimental realization of SOT switching to date requires an additional in-plane magnetic field, or other more complex measures, thus severely limiting its prospects. Here we present a novel structure consisting of two heavy metals that delivers competing spin currents of opposite spin indices. Instead of just canceling the pure spin current and the associated SOTs as one expects and corroborated by the widely accepted SOTs, such devices manifest the ability to switch the perpendicular CoFeB magnetization solely with an in-plane current without any magnetic field. Magnetic domain imaging reveals selective asymmetrical domain wall motion under a current. Our discovery not only paves the way for the application of SOT in nonvolatile technologies, but also poses questions on the underlying mechanism of the commonly believed SOT-induced switching phenomenon.

中文翻译：

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通过竞争自旋电流切换垂直铁磁层

自旋电子学的最终目标是通过电气手段控制磁力。一种有前途的方法是利用源自重金属及其界面的强自旋轨道耦合的电流感应自旋轨道转矩（SOT）在室温下切换单个垂直磁化​​的铁磁层。然而，迄今为止，SOT开关的实验实现需要附加的面内磁场或其他更复杂的措施，因此严重限制了其前景。在这里，我们介绍了一种由两种重金属组成的新颖结构，该结构可提供自旋指数相反的竞争自旋电流。不仅仅是像人们期望的那样消除纯自旋电流和相关的SOT，并得到了广泛接受的SOT的证实，这样的设备表现出仅通过平面内电流而没有任何磁场即可切换垂直CoFeB磁化的能力。磁畴成像揭示了在电流作用下选择性的非对称畴壁运动。我们的发现不仅为SOT在非易失性技术中的应用铺平了道路，而且对人们普遍认为SOT引起的开关现象的潜在机理提出了疑问。