论文标题
电流引起的扭矩起源于轨道电流
Current-induced torque originating from orbital current
论文作者
论文摘要
通过电流诱导的自旋扭矩对磁化的电气操作使实现了多种超低功率和快速的自旋设备,例如非挥发性磁性记忆,旋转旋转纳米示波器和神经形态计算设备。最近的进步导致了一个观念,即相对论自旋 - 轨耦合是电流诱导的扭矩的有效来源,开放了自旋甲循环的领域。然而,尽管取得了重大进展,但磁化操纵的基本机制,即自旋电流在产生电流引起的扭矩中的要求保持不变。在这里,我们在不使用自旋电流的情况下演示了电流引起的扭矩的产生。通过测量自然氧化的-CU/铁磁 - 金属双层的电流诱导的扭矩,我们观察到尽管没有强旋转轨道耦合,但在低温下,在低温下有异常高的自旋霍尔电导率。此外,我们发现扭矩的方向取决于铁磁层的选择,这反应了对电流诱导的扭矩的常规理解。这些非常规的特征最好用自旋扭矩的轨道对应物(轨道扭矩)来解释,这是轨道rashba效应和轨道电流产生的。这些发现将阐明电流诱导的磁化操纵的潜在物理,从而有可能改变旋转轨道的景观。
The electrical manipulation of magnetization by current-induced spin torques has given access to realize a plethora of ultralow power and fast spintronic devices such as non-volatile magnetic memories, spin-torque nano-oscillators, and neuromorphic computing devices. Recent advances have led to the notion that relativistic spin-orbit coupling is an efficient source for current-induced torques, opening the field of spin-orbitronics. Despite the significant progress, however, the fundamental mechanism of magnetization manipulation, the requirement of spin currents in generating current-induced torques, has remained unchanged. Here, we demonstrate the generation of current-induced torques without the use of spin currents. By measuring the current-induced torque for naturally-oxidized-Cu/ferromagnetic-metal bilayers, we observed an exceptionally high effective spin Hall conductivity at low temperatures despite the absence of strong spin-orbit coupling. Furthermore, we found that the direction of the torque depends on the choice of the ferromagnetic layer, which counters the conventional understanding of the current-induced torque. These unconventional features are best interpreted in terms of an orbital counterpart of the spin torque, an orbital torque, which arises from the orbital Rashba effect and orbital current. These findings will shed light on the underlying physics of current-induced magnetization manipulation, potentially altering the landscape of spin-orbitronics.