Antiferromagnet (AFM)/ferromagnet (FM) systems such as IrMn/CoFeB/MgO enable spin–orbit-torque- (SOT-) induced switching of perpendicular magnetization in the absence of an external magnetic field. However, the low thermal stability, weak perpendicular magnetic anisotropy (PMA), and indistinctive SOT of these AFM/FM heterostructures pose challenges to the practical application. Here, through the insertion of a thin W layer between the IrMn and CoFeB layers, we show that much larger effective PMA fields are obtained with annealing stability to 300 °C, which is guaranteed by the prevention of Mn diffusion via W insertion as shown in spherical aberration corrected transmission electron microscopy and atomic-resolution electron energy-loss spectroscopy measurement results. Furthermore, the spin–orbit torque is effectively tuned by changing the W layer thickness via modulation of the interfacial spin–orbit coupling at IrMn/W/CoFeB interfaces, which was reported to degrade the interface spin transparency for the spin currents. Finally, field-free magnetization switching was achieved with comparable exchange bias fields to samples without W insertion. This work demonstrates an effective strategy for improving the performance of the thermally robust AFM-based SOT device.

中文翻译：

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通过原子厚的钨插入调节 IrMn/CoFeB/MgO 结构中的热稳定性和自旋轨道扭矩

反铁磁体 (AFM)/铁磁体 (FM) 系统，例如 IrMn/CoFeB/MgO，可以在没有外部磁场的情况下实现自旋轨道扭矩 (SOT-) 感应的垂直磁化切换。然而，这些 AFM/FM 异质结构的低热稳定性、弱垂直磁各向异性 (PMA) 和模糊的 SOT 给实际应用带来了挑战。在这里，通过在 IrMn 和 CoFeB 层之间插入薄的 W 层，我们表明获得了更大的有效 PMA 场，退火稳定性达到 300 °C，这是通过 W 插入防止 Mn 扩散来保证的，如图所示球差校正透射电子显微镜和原子分辨率电子能量损失光谱测量结果。此外，通过调节 IrMn/W/CoFeB 界面处的界面自旋轨道耦合来改变 W 层厚度，从而有效地调节自旋轨道扭矩，据报道，这会降低自旋电流的界面自旋透明度。最后，通过与没有 W 插入的样品相当的交换偏置场，实现了无场磁化切换。这项工作展示了一种提高基于 AFM 的热稳健 SOT 设备性能的有效策略。